Chapter 1 Mishna 16
פרק א משנה טז

Rabban Gamliel would say: make for yourself a Rav, and remove yourself from doubt, and do not frequently Maaser (tithe) by estimation.
רַבָּן גַּמְלִיאֵל הָיָה אוֹמֵר, עֲשֵׂה לְךָ רַב, וְהִסְתַּלֵּק מִן הַסָּפֵק, וְאַל תַּרְבֶּה לְעַשֵּׂר אֹמָדוֹת:


~Level 1~
Bartenura - "make for yourself a Rav" - he is now speaking on horaah (halachic rulings). If a din (halachic question) comes before you and you are in doubt on it, make for yourself a Rav.

"and remove yourself from doubt" - and do not rule on it by yourself..

"do not frequently Maaser (tithe) by estimation" - for one who separates maaser (tithe) by estimate is not saved from corrupting. If he separates less than a tenth, his maaser is rectified, but his fruit are bungled (mixed with tevel). Likewise, if he separates more than a tenth for maaser, his fruit are rectified but his maaser is bungled (mixed with tevel).
~Level 1~
Rashi - "Rabban Gamliel would say" - this is Rabban Gamliel the son of Rebbi Shimon the son of Hillel.

"make yourself a Rav" - I explained this earlier in Mishna 6.

"remove yourself from doubt" - if you learn by yourself, you will have many doubts. Alternatively, do not decide Halacha for yourself and stand confidently [by your ruling]. Rather, since it (the Halacha) is not explicitly stated, one needs to go to his Rav, as explained in Yevamot 109b, see there.

"remove yourself from doubt" - that you not have a doubt in your heart regarding the foundation of the foundations (yesod haesodot) or the knowledge of the secrets (yediat hasodot). Rather, it should be with certainty and confirmed in the eye of the heart. For this is the primary thing.

"do not frequently Maaser (tithe) by estimation" - do not maaser (tithe) by estimating for sometimes it will not be well estimated, like a person who does not learn from the Received Tradition (oral law from a Rav).
~Level 2~
Rabeinu Yonah - "do not frequently Maaser (tithe) by estimation" - to not maaser by estimate.. for one who maasers by estimate, his fruit are rectified, but his maaser is bungled (mekulkal). For example: let's say he separated maaser generously, the extra amount over a tenth which he separated is tevel, not maasered, until he maasers that extra amount. Thus, if he does not notice to do so, his maaser has a bungle (kilkul).

This matter is an analogy for a logical argument (svara). A man should not do it approximately. Rather, the primary way is to plumb to the full depth of the knowledge (yered le sof hadaat). For not all logical arguments are equal. Some have two sides. Even though one wise man's logic (svara) leans to one side, but he understands and recognizes that a different wise man can also say a different argument in this, only that this way appears more right in his eyes. Sometimes a wise man conceives a logical argument of his own and thinks it is irrefutable by sound reason and there is no other way to see it and no other wise man who would possibly argue with him. The understanding person will understand. This is why he brought this analogy after "make for yourself a Rav and remove yourself from doubt", which are also regarding rational argument (svara).
~Level 2~
Likutim - why did it not say right away: "Rabban Yochanan ben Zakai received from Hillel..." (but instead mentions it later in Avot 2:8)? [answer:] It was for the honor of Hillel and his seed. For after Hillel, Rabban Yochanan ben Zakai was the Nassi (head leader) for forty years. After that, the title of Nassi returned to the royal seed. Thus, Rebbi (who wrote the mishna) did not want to interrupt the order of his yichus (ancestry) with Rabban Yochanan ben Zakai. Although he was humble, he was careful (makpid) for the honor of the Nessiot, as we find written: "who are these people? They are people who seek to uproot your honor and the honor of your father's house.." (Horayot 14a)
~Level 2~
Rambam - Mishne Torah Sanhedrin 20:8 - any judge who begins comparing a judgment that is brought before him to a judgment that was already rendered with which he was familiar is considered as wicked and haughty when rendering judgment if there is a scholar in his city who is wiser than him and he fails to consult him. Our Sages comment: "May evil upon evil befall him." For these and similar concepts stem from haughtiness which leads to the perversion of justice.
~Level 2~
Chida - Chasdei Avot - the Rambam (Sanhedrin 20:8) and Tur (Choshen Mishpat s.62) wrote that it is not only one's own Rav. Rather, if there is a talmid chacham in the city, you must ask him. Likewise, the Maharshal writes in the Yam Shel Shlomo there and in teshuva siman 35. Rabeinu Yerucham writes in the Sefer Mesharim (Netiv 1, chelek 2): "if there is a talmid chacham in the city, a judge is not allowed to judge a doubtful matter before asking him. [Namely,] comparing one thing to another, unless it is clear to him as the morning [light]." end quote.

This implies, if it is clear to him, there is no shayla (question).

Perhaps this is the meaning of "make for yourself a Rav and remove yourself from doubt", i.e., this is when you have a doubt - then make for yourself a Rav. But if the matter is clear to you, then you may judge using your own judgment and you don't need to ask a Chacham, as Rabeinu Yerucham.
~Level 2~
Rabbi Avraham Azoulai - Ahava b'Taanugim - earlier in mishna 6, he exhorted "make for yourself a Rav" regarding learning, namely, that one's [Torah] wisdom be received from those earlier than him. But here, he exhorts on the matter of halachic rulings (hora'ah). Namely, that if one learns from many sages, his rulings are not reliable. This is as our sages said on Rav Yehuda: "one shoud not rely on his hora'ah because he learned from everyone".

Alternatively, some explain that if a hora'ah comes to you that is not clear from the talmud and you need to decide by logic (svara), make for yourself a Rav, in order to clarify the matter, and "remove yourself from doubt" and do not be embarrased to ask. And even if you dont find anyone as big as yourself to ask, ask even one smaller than yourself.

Perhaps it will be clear to him through some teaching he heard. And even if it is not clear to anyone and you are forced to rule by svara (reason), "make yourself a rav" so that the entire punishment of the doubt not be on you alone. Rather, join in others and make him a Rav on you even if they are not so. In order that each one receive only a small portion of the punishment. (see Sanhedrin 7b).

"do not frequently Maaser by estimation" - do not habitually rule in that which is not clear from the talmud using your own estimation and logic (omed v'svara).

Rather, investigate the books of Halachot until you find help and support to your words.
~Level 3~
Chasdei David - "make for yourself a Rav" - it is the way of the world that when there is a doubt on issur v'heter (ex. mixtures of meat and milk), one immediately goes to ask a Rav, even though most of the time it is only a distant concern (chashash rachok) and it does not really even enter into the category of a "question" (Shayla). For example, "noten taam lepagam" or "kli sheni". The concern is at most a Rabbinical doubt (safek d'rabanan).

But for matters between man and his fellow such as "words that hurt" (onaat devarim) which have a biblical prohibition as written: "you shall not wrong, one man his fellow" (Vayikra 25:17), which the talmud expounds: "this refers to 'words that hurt' (onaat devarim)" (Bava Metzia 58b). The talmud explains there:

"What is the case of 'words that hurt' (onaat devarim)? If he were a baal teshuva (penitent), do not tell him: 'remember your previous deeds', or if he were a convert coming to learn Torah, do not tell him: 'the mouth who ate unkosher meat should now learn Torah??'" end quote.

Likewise for onnat mamon (monetary oppression) or embarassing one's fellow - no one opens their mouth to ask! This is "make for yourself a Rav", that you ask a Rav for matters people are lax in, namely, matters between man and his fellow, and "remove yourself from doubt", i.e. refrain from things which have a trace of doubt.
~Level 3~
Maharal - it is proper to ask: what do these three things have to do with each other?

Another question: "make for yourself a Rav" was already said earlier by Yehoshua ben Perachya (Mishna 6).

Know that Rabban Gamliel came to give mussar to a man that all his matters be clear till there is no doubt in them. For when one's actions contain doubt, he is not called a baal sechel (possessor of intellect). For regarding the sechel (intellect), all its matters are clear, without doubt.

On the fool it is written: "the fool walks in darkness" (Kohelet 2). But for a man who wants to be a baal sechel, his matters will be clear. And if a man goes out of this trait, it is as if he goes out of the boundary of a human, who is a baal sechel (possessor of intellect).

Doubt can occur to man in three areas.

One, in his sechel (intellect), when the matter is not clear, and he has sides (panim) to here and to here.

Two, for all matters where one is in doubt due to lack of knowledge and which do not depend at all on intellect.

Three, doubts a man has regarding the performance of mitzvot, [namely] when the performance of the mitzah is not clear.

We will further explain these three later on.

Corresponding to the first, he said "make for yourself a Rav", so that what one acquires of wisdom is something clear, without doubt.

"remove yourself from doubt" - i.e. from every thing which one is in doubt.

Regarding forbidden things (issur), it is certainly superfluous to say. For "safek issur l'chumra" (a doubtful prohibition is treated stringently).

Rather the intent is that for everything which may possibly lead to damage (hezek), one should not at all enter in the doubt. For this is not proper for a baal sechel (possessor of intellect) to enter in a doubt.

Corresponding to the third, he said to not frequently "Maaser (tithe) by estimation", ie to not rely on estimates in the performance of mitzvot.

And even though the Torah permitted this, as brought in Bechorot (58b): "just as Terumah Gedolah may be set apart by estimating so too Terumah Maaser..."

Thus, even though Terumat Maaser has a fixed amount of a tenth, one may separate it by estimate, and all the more so for Maaser. But nevertheless, do not frequently Maaser by estimate, in a habitual manner. Only when it is necessary and one does not have time, then it is permitted.

And even if the estimate is close to exact, nevertheless, remove yourself even from this. For it is only proper for a man that all his deeds be clear, removed from doubt.

Because thus is proper for a possessor of intellect (baal sechel) to not walk in darkness.

And certainly when he conducts himself in this trait, it is a great perfection (shlemut) for him. For many, many lackings follow when a man's deeds are not clear.

Furthermore, this trait is proper for a possessor of intellect (baal sechel), that his deeds stem from a clear intellect..
~Level 3~
Some explanations on the order of the Mishna in this chapter
Maharal - Why did the mishna not say "Rabban Gamliel received..." (but instead just "Rabban Gamliel would say")?

He did not say here [Rabban Gamliel] "received". For the Tradition (kabala) continued (intact) only until Hillel and Shammai, as written in the Talmud "when the disciples of Shammai and Hillel, who had insufficiently studied, increased [in number], disputes multiplied in Israel, and the Torah became as two Torahs" (Sanhedrin 88b). Therefore, he did not say "received" (kabala) after Hillel and Shammai.

(Translator: Some important background info. According to Rambam's introduction to Mishneh Torah, here is the order of transmission after Hillel and Shammai:
1. Rabban Yochanan ben Zakkai and Rabban Shimon the son of Hillel received from Hillel and Shammai.
2. Afterwards, Rabban Gamliel HaZaken ben Rabban Shimon
3. Afterwards, Rabban Shimon (son of 2.)
4. Afterwards, Rabban Gamliel II (son of 3.)
5. Afterwards, Rabban Shimon ben Gamliel (son of 4.)
6. Afterwards, Rebbi Yehuda HaNassi (son of 5., this is Rabeinu HaKadosh compiler of the mishna)
7. Afterwards, Rabban Gamliel III (son of 6., brought next chapter)
back to Maharal...)

The mishna here also did not mention Rabban Shimon, the son of Hillel, and instead skipped to Rabban Shimon's son - Rabban Gamliel (grandson of Hillel).

Likewise, later it does not mention Rabban Gamliel (#4, the grandson of Rabban Gamliel HaZaken #2) who was the father of Rabban Shimon ben Gamliel (#5) in the last mishna who said "on three things the world stands..".

All of them were Nesiim (chief leaders), as brought in the talmud "Hillel, Shimon, Gamliel, and Shimon assumed their Nassi position for 100 years during the temple" (Shab.15a).

It seems the reason the Mishna did not mention Rabban Shimon (#1), the son of Hillel, is because during his time, Rabban Yochanan ben Zakai was also a leader and as great as him. For everywhere it says: "when the temple was destroyed Rabban Yochanan ben Zakkai decreed.."

Rabban Yochanan ben Zakkai was a disciple of Hillel. Thus he was also a leader and Nassi, and it is not possible to mention both of them. For they were not of the pairs whereby one was Nassi and the other was Av Beit Din. Therefore, he mentioned neither. For which one should he mention?

Likewise in the time of Rabban Gamliel (#4) father of Rabban Shimon ben Gamliel (#5), there was Elazar ben Azarya who was also Nassi, as brought in Berachot (28a) (therefore he was also not mentioned in this chapter)...
(Translator: the Maharal will give another reason for this in Mishna 18. see there)
~Level 4~
Ben Ish Chai - Chasdei Avot - "make for yourself a Rav" - it is known why the sages (Chachamim) are called "Talmidei Chachamim" (disciples of sages) everywhere, and as they said: "Talmidei Chachamim bring Shalom to the world", and likewise in hundreds of places, whether when referring to single individuals or many [sages].

The reason for this is in order to teach that even if a man toiled in Torah for 80+ years, nevertheless, it is proper for him to conduct himself as a disciple. Namely, that he learns from his colleagues and even from his students. And even if he learned from many Rabbis, he should not be satisfied with this. Rather, whenever he can find a wise man (chacham) to learn from, he should do so. He should not have the trait of Histapkut (being satisfied with little) in this.

Thus, "make for yourself a Rav", always, all your days, seek a Rav to teach you. For it is not possible that you will not find a new Chidush (insight) that you did not know and you will learn it from him. And as Ben Zoma said: "who is wise? he who learns from every person" (Avot 4:1).

In this matter of study which I commanded you to learn from every person and make a new Rav always - "remove yourself from doubt (Safek)" - from the word "Histapkut" (contentment), ie do not have Histapkut (contentment) in this matter saying: "I already learned from several Rabbis and received from them many kabalot (teachings). It is enough for me these sages I learned and received from. Rather consider yourself that all you learned is not enough for you and you are still in the category of "disciple" (talmid) who needs to learn from others.