What are the connotations of "Ve'ahavta es Hashem ... "?
Rashi #1: It means that one should serve Hashem not (only) out of fear but also out of love. 1
Rashi #2 (in Sanhedrin, 74a): It means that one should not exchange Him for any other god.
Ramban (citing the Sifri): One should not study Torah (in order to be called 'Rebbi', to sit in a (prestigious) Yeshivah, to live a long life or to merit Olam ha'Ba); rather, out of love of Hashem.
Seforno: It means that one should be happy to do whatever is good in the Eyes of Hakadosh-Baruch-Hu.
Hadar Zekenim (5:1): You should love Him like the Avos did. It says about Avraham "u'Matzasa Es Levavo Ne'eman Lefanecha" (Nechemyah 9:8), Yitzchak was Moser Nefesh to be a Korban to Hashem, and Yakov accepted to tithe to Hashem all that he will get (be'Chol Me'odecha) - Bereishis 28:22.
Mesilas Yesharim (Perek 19): The test of love is [serving even] at a time of hardship and affliction.
Targum Yonasan: 'Follow the true worship of yyour fathers and love Hashem ... '?
If one should serve Hashem purely out of love, why did the Torah write earlier (4:40) "Lema'an Yitav lach ... " and "u'Lema'an Tichyu Uva'sem vi'Yerishtem es ha'Aretz"?
Ramban: It is in the form of a warning - that if we don't keep the Mitzvos, we will forfeit our rights to live, or to continue to live in Eretz Yisrael. It is not the reason to observe the Mitzvos!
Since the Torah will say (in Pasuk 13) "Es Hashem Elokecha Tira", why does it need to add "Ve'ahavta ... "?
Rashi: Because someone who serves his master out of fear will desert him if he pressurizes him excessively, which he will not do if he serves him out of love. 1
Ramban (citing the Yerushalmi in Berachos, 9:5): 'Serve both out of love and out of fear - Out of love, because someone who loves will not hate; out of fear, so that, in the event that you come to lash out, you will not lash out!' 2
What are the implications of "be'Chol Levavcha"?
Rashi #1 (citing Brachos 54a) and Targum Yonasan: It implies that should serve Hashem with the Yeitzer ha'Ra as well as with the Yeitzer ha'Tov. 1
Ramban: It implies that one should control the desires of his heart due to the love of Hashem. 4
Ramban (citing the Ibn Ezra): You should love Hashem with your mindset. 5
Which we learn from the second 'Veis' in "Levavcha". See Sifsei Chachamim. In other words, to harness one's bad Midos - such as Ta'avah (desire) in the service of Hashem (See also commentary of Mosad ha'Rav Kook) and Ba'al ha'Turim.
It also implies that one should serve Hashem without doubts - See Peninim mi'Shulchan ha'Vilna Gaon, Bereishis, 4:5-7.
Which we learn from the word "be'Chol". See also commentary of Mosad ha'Rav Kook.
What are the implications of "be'Chol Naf'sh'cha"?
Rashi (citing Berachos, 54a) and Targum Yonasan: It implies that one should love Hashem even if He takes one's life. 1
Ramban #1: It implies that one should also love Hashem with one's mind. 2
Ramban #2 (citing the Ibn Ezra): You should give up your desires on account of your love of Hashem]. 3
In other words, one should be prepared to give up one's life for the love of Hashem. Ramban: According to this explanation, either the words "be'Chol Nafshecha" are superfluous, or it means even going so far as to give up one's life, as opposed to merely suffering or giving up a single limb, which is like half one's soul..
Ramban: As in Shmuel 1, 25:29. And it means to have the correct Hashkafos - in matters concerning Emunah and Bitachon.
What are the implications of "be'Chol Me'odecha"?
Rashi #3 (in Sanhedrin, 74a): "be'Chol Naf'sh'cha u've'chol Me'odecha" implies that one's love of Hashem should override everything that one holds dear.
Ramban: It implies that one's love for Hashem should be intense. 5
Ramban: The Torah tends to refer to one's money as 'an abundance' - See Ramban.
Rashi (citing Berachos 61b): Even though it already obligates giving up one's life for Hashem, some people love their money more their bodies. See Sifsei Chachamim. One is obligated to give up all one's money to avoid transgressing a Lo Sa'aseh, but for an Asei, only a fifth.
Rashi: be'Chol Midah u'Midah she'Hu Moded lo, hevei Modeh Lo Me'od Me'od' - a play on the word "Me'odecha".
Rashi: As David ha'Melech said in Tehillim, 116:13, 3 & 4 "Kos Yeshu'os Esa u've'Shem Hashem Ekra", and "Tzarah ve'Yagon Emtza; u've'Shem Hashem Ekra!"
Ramban: As if it had written "Me'od Me'od".
Rashi (citing Brachos 54a) writes that one must serve Hashem with the Yeitzer ha'Ra and the Yeitzer Tov. How does one do so?
R. Yonah (Al ha'Rif, Brachos 44b) #1: Avodah of the Yeitzer Tov is doing Mitzvos. Avodah of Yeitzer ha'Ra is overcoming it. 1
R. Yonah (Al ha'Rif, Brachos 44b) #2: The Yeitzer Tov is Midos such as mercy. The Yetzer ha'Ra was created for cruelty. When a person is not merciful on Resha'im and is cruel to them, he does a great Mitzvah and serves Hashem with the Yetzer ha'Ra.
Lev Eliyahu (Shemos p.192): Also eating, drinking and sleeping, from which comes evil, also with them one can serve Hashem, to do everything l'Shem Shamayim.
QUESTIONS ON RASHI
Rashi writes that we need b'Chol Me'odecha, for some people love their money more their bodies, "V'Chol Asher la'Ish Yiten Be'ad Nafsho" (Iyov 2:4)! And one who forfeits his life, he loses all his money!
Kol Eliyahu, Divrei Eliyahu: Rashi cites R. Eliezer, who discusses how much people exert for Mitzvos. Some prefer bodily toil, and some prefer to spend their money; the Torah obligates both. R. Akiva argues, and teaches that b'Chol Nafshecha obligates giving one's life. His Talmidim did not understand how he accepted Ol Malchus Shamayim during his excruciating execution 1 , for they held like R. Eliezer.
How is this relevant? R. Akiva did not have a choice to live at the time! Perhaps they asked why he openly taught Torah and brought this on himself.Or, they thought that if he retracts, they will lighten his death (PF)