Gemara

(Mishnah): She (Munvaz' mother) made a gold tablet on which Parashas Sotah was written (the Kohen would copy it onto a parchment for Hashka'as Sotah).

Gitin 60a - Rabah and Rav Yosef: We may not read a Sefer Haftorah (a scroll containing only the Parshiyos of Nevi'im read for the Haftorah), for one may not write an incomplete Sefer.

Mar bar Rav Ashi: Since one may not read from it, one may not even move it on Shabbos!

Rejection: The Halachah does not follow these opinions. Rather, we may move and read from it:

R. Yochanan and Reish Lakish read from a Sefer of Agadata on Shabbos.

Question: It is forbidden to write Torah she'Ba'al Peh!

Answer: Since there was no alternative (the teachings were in danger of being forgotten), they could be written - "Es La'asos la'Shem Heferu Torasecha".

Similarly, we may write and use a Sefer Haftorah (since congregations cannot afford complete Nevi'im).

Question (Abaye): May one write a Megilah (partial Chumash) to teach a child?

We ask according to the opinion that the Torah was given Parashah by Parashah (Moshe wrote each Parashah when he learned it), and also according to the opinion that the Torah was given complete.

According to the opinion that the Torah was given Parashah by Parashah, we should likewise be allowed to write one Parashah;

Or perhaps, Kiven d'Idbak, Idbak (once the Torah was completed, it can no longer be written piecemeal)!

According to the opinion that the Torah was given complete, likewise, we may only write complete Seforim;

Or perhaps a Megilah is permitted, since there is no alternative (for people that cannot write a full Sefer).

Answer #1 (Rabah): According to both opinions, it may not be written.

Question - Mishnah: She made a gold tablet on which Parashas Sotah was written.

This shows that one may write a Megilah to teach a child (just like it was permitted for Sotah)!

Answer (Reish Lakish): Only the first letter of each word was written.

Question (Beraisa): The Kohen (who writes Parashas Sotah) looks at the tablet and writes (exactly) what is written in the tablet.

Answer: It means, he writes according to what is written in the tablet.

Question (Beraisa): When he writes, he looks and writes what is written in the tablet;

In the tablet it says "If a man lied with you...if he did not lie..."

Answer: The tablet was written b'Seirugin (Rashi - the first words of each verse are written, and the initial letters of the last words).

Answer #2: Tana'im argue about whether or not one may write a Megilah to teach a child:

Beraisa: One may not write a Megilah to teach a child unless he will complete the Sefer;

R. Yehudah says, one may write from "Bereishis" until the Dor ha'Mabul, or from "Vayikra" until "Uva'Yom ha'Shemini".

Rishonim

Rif and Rosh (Gitin 27b and 5:20): R. Yochanan and Reish Lakish read from a Sefer Agadata because of "Es La'asos la'Shem". A Sefer Haftorah is similarly permitted.

Rif (ibid.): The Halachah is that one may write a Megilah to teach a child.

Question (Rosh, ibid.): Rabah forbids this, and no one argues with him. Also, we should rule like Chachamim of the Beraisa, who forbid!

Answer (Rosh, ibid.): Perhaps the Rif rules like R. Yochanan, who says that the Torah was given Parashah by Parashah. The Gemara said that R. Yochanan could agree that once the Torah was completed one may not write a Megilah, but this is not really so. If it was, also writing a single Chumash would be forbidden! Alternatively, the Rif is lenient because there are Aniyim who cannot afford to write a Sefer Torah for their children.

Rebuttal (Beis Yosef OC 283 DH u'Devarav): Rabah said that even R. Yochanan forbids. Abaye accepted this, and no one argued. How can the Rif argue? Even if the Rif had a question he could not answer (if we say Kiven d'Idbak, why may one write a Chumash?), this does not justify ruling unlike the Amora'im! Also, the question can be answered! Each Chumash is an entity unto itself, therefore it may be written alone. Abaye asked whether we can be lenient because Aniyim cannot afford an entire Sefer Torah, and Rabah answered negatively. We cannot override Rabah for this very reason!

Defense #1 (Beis Yosef DH veha'Ran): Perhaps in the days of Rabah and Abaye four or five Aniyim could learn together from one Sefer Torah. Even though this is difficult, it is not "Es La'asos la'Shem" to justify writing a Megilah. However, in the days of the Rif there was not even one Sefer for 10 children. It was "Es La'asos", for without Megilos children would not learn.

Defense #2 (Beis Yosef, ibid.): Rabah forbids Sefer Haftorah. The Halachah does not follow him, because "Es La'asos la'Shem".

Rambam (Hilchos Sefer Torah 7:14): It is permitted to write a single Chumash. It does not have the Kedushah of a Sefer Torah. One may not write a Megilah with Parshiyos or to teach a child, unless he plans to complete the Chumash. If a Megilah has three words in every line it is permitted.

Beis Yosef (DH v'Chosav ha'Rambam): The Gemara answered that Parashah Sotah was written on the tablet b'Seirugin. The Rambam (in a Teshuvah) explains that there are three words on a line, and the words on each line are far from those on the next line. He also says that if one must write a verse he should write at most three words. If he needs the entire verse he should write Simanim in place of the words, or write just one or two letters of each word, or write b'Seirugin.

Poskim

Shulchan Aruch (YD 283:2): One may not write a Megilah by itself with Parashiyos. One may not write one for a child to learn from. If he plans to complete the Chumash it is permitted.

Taz (1) and Shach (3): The custom is like those who permit because of "Es La'asos la'Shem". Otherwise, people would be Batel from learning and prayer. It is improper to write verses on the wall for a good Mazel, for the Torah was given complete.

Bach (DH Rav Alfas): The custom everywhere is to write any matter of Torah or Tefilah if there is danger that it will be forgotten.

Aruch ha'Shulchan (11): The Taz permits only for the sake of learning; the Shach and Bach disagree. However, nowadays that everything is printed, it makes no difference. The Halachah follows the Rambam, and only a complete Chumash may be printed (i.e. since Seforim are inexpensive, it is no longer "Es La'asos la'Shem").

Question: The Isur of a partial Sefer should not apply to Nevi'im and Kesuvim, for these were not given 'Chasumah', However, Rashi explains that Sefer Haftorah is forbidden (if not for "Es La'asos la'Shem") because also Nevi'im must be complete!

Answer (Aruch ha'Shulchan 13): We learn from Torah to Nevi'im.

Shulchan Aruch (3): If a Megilah has three words in every line it is permitted.

Taz (2): The words on each line are far from those on the previous line, so they are not read together. It is permitted because it does not look like one Megilah.

Shulchan Aruch (4): It is forbidden to embroider verses on a Talis.

Beis Yosef (DH v"Chosav Od Sham): This is because one may not write even one verse. Also, a Talis is Tashmishei Mitzvah without Kedushas ha'Guf, so one may enter a bathroom or Mikveh with it, or use it to cover Ervah. One may not write a verse anywhere where it will come to disgrace.

Shach (6): Since the mantle for a Sefer Torah has Kedushas ha'Guf, it is the custom to write verses on it. R. Yerucham forbids because one may not write even one verse, but it has become widespread to be lenient.