Gemara

(Beraisa #1 - R. Akiva) Question: What do we learn from "v'Hishkah (he will give her to drink)" (Bamidbar 5:24, before offering the Minchah)? It 'already' says "v'Hishkah" (after it is offered, 5:27)!

Answer: If the scroll was erased and she refuses to drink, we force her to drink.

Contradiction (Beraisa #2 - R. Yehudah): If she refuses to drink after the scroll was erased, we pour the water down her throat against her will;

R. Akiva says, we do not give her to drink. Drinking is only to test her, and we know (by her refusal) that she is guilty! Rather, she can refuse to drink only before offering the Kometz, but not afterwards.

Counter-question: Beraisa #2 itself is difficult! R. Akiva says that she cannot refuse after offering the Kometz. If she refuses to drink, we know she is guilty, so she should not drink!

Answer: A calm refusal to drink shows that she is guilty, so she does not drink. If she refuses to drink from fear, before the Kometz was offered, since the scroll was not yet erased (even if it was erased, this was improper), she can refuse. After the Kometz was offered, since the scroll was erased properly, she cannot refuse.

The contradiction remains! (In Beraisa #1, R. Akiva holds that she cannot refuse, even before the Kometz was offered. In Beraisa #2, he allows her to refuse then!)

Answer: The Tana'im of the two Beraisos argue about R. Akiva's opinion.

Question: If she calmly refused to drink, and later she wants to drink, can she?

Perhaps she already established her guilt, so she may no longer drink;

Or, since now she wants, this shows that her initial refusal was due to fear!

This question is unresolved.

20a (Mishnah): If she refuses to drink before the scroll was erased, we bury the scroll and spread her Minchah (on the ashes). If after the scroll was erased she says that she is Temei'ah, we spill the water and spread her Minchah. If she refuses to drink after the scroll was erased, we force her to drink against her will.

23a (Mishnah): If she refuses to drink or her husband does not want her to drink, the Minchah is burned.

Yevamos 95a: If a man said that he will not give his wife (a Sotah) to drink, she is (permanently) forbidden to the Bo'el.

Rishonim

Rambam (Hilchos Sotah 2:1): If one said that he will not make his wife drink, she does not drink, She is divorced with a Kesuvah and is forbidden to him forever.

Rambam (4:3): If a Sotah refused to drink due to fear, she can retract and decide to drink. If she was not afraid and refused to drink, she cannot retract.

Kesef Mishneh: We learn (the latter law) from Sotah 19.

Gilyon R. Akiva Eiger: The Gemara did not settle the question!

Rashi (20a DH v'Chozrah): The question about whether she can retract (if initially she calmly refused to drink) and say that she will drink is according to R. Akiva.

Sefas Emes (DH Omrah): Seemingly, we could ask according to everyone, before the Megilah was erased! The Rambam rules that she cannot retract. Perhaps he is unsure, and does not let her drink for it will not permit her to her husband. Or, the Rambam is sure that she may not drink, even though the Gemara said 'Teiku'.

Keren Orah (20a DH Iba'i): Rashi holds that according to Chachamim, refusal to drink is not an admission, so surely she can retract. What is the Rambam's source that Chachamim distinguish between calmness and fear?

Rambam (4): If she refuses to drink before the scroll was erased, we bury the scroll. If she refuses after the scroll was erased, we force her to drink.

R. Akiva Eiger: This is when she retracted after a refusal due to fear. If she refused to drink not due to fear, this is like an admission of guilt, and we do not give to her to drink. This follows from the Gemara.

Tosfos (20a DH Megilasah): In the Yerushalmi, Beis Shamai say that we force her to drink if one letter was erased. Beis Hillel force her if two letters were erased, for this is enough to write Yud-Kei.

Shirei Korban (15a DH Kamah): We force her to drink for causing Hash-m's name to be erased. Why should we force her for one letter of the Megilah? It is not part of His name!? Rather, they discuss how many letters of His name were erased. Why did the Rambam omit this, and just cite the Mishnah?

Minchas Chinuch (365, ha'Shniyah DH v'Ayen): Why did the Rambam omit this? He connotes that we force her only if the entire Megilah was erased!

Rashi (20a and Bartenura 3:3 DH Me'ararin): We force her to drink because perhaps she is innocent, and refuses to drink due to fright.

Tosfos Yom Tov (DH Me'ararin): They establish the Mishnah like R. Akiva. Alternatively, it is like R. Yehudah, who forces her to drink in any case. They explain why we force her: even if she appears calm, perhaps she is afraid.

Tosfos (Yevamos 95a DH Ileima): Our Gemara says that if he does not want her to drink, she is forbidden forever. This is because he cannot retract. Our Gemara learned from Sotah 23a: if he does not want her to drink, the Minchah is burned.

Question #1 (Aruch l'Ner): The Tosfos Yom Tov (1:3) observed that Mishnayos 1:3 and 3:6 say that she may not eat Terumah and her Minchah is burned when her husband does not want to make her drink. Mishnah 4:2 says that she gets a Kesuvah if he says 'I will not make her drink.' This implies that had he said only 'I do not want', he can retract!

Question #2 (Avnei Milu'im 11:1): Perhaps he can retract. We burn the Minchah due to Dichuy (when he said that she will not drink, the Minchah was unusable. Amora'im argue about animals, but all agree that Dichuy applies to Menachos! Dichuy does not apply when one can make the Korban usable again. However, it is her Korban, and she cannot make him retract!

Question #3 (Keren Orah DH Shuv): If we could learn from 23a, we should also settle the question that she cannot retract and drink!

Minchas Chinuch (ibid. DH ul'Aniyas): If her husband does not want her to drink, this is like admission (that the water will not work, for he transgressed Isurei Bi'ah). This is why he cannot retract. It seems that even after the Megilah was erased he can refuse to make her drink; no one distinguishes.

Note: This is not clear to me. Perhaps he planned to divorce her in any case, and did not want Hash-m's name to be erased. Or, he did not want her (or the Bo'el) to die if she was Mezanah. (A man might even scheme and write an undated Get to save his wife from execution - Gitin 17a.) Or, he wanted to avoid shame to himself and/or her (a Sotah is disgraced in the Mikdash)!