Comentário sobre Deuteronômio 24:4

אחרי אשר הטמאה [HER FIRST HUSBAND … MAY NOT TAKE HER AGAIN TO BE HIS WIFE] AFTER THAT SHE IS DEFILED — these words are intended to include in the prohibition a faithless wife (סוטה) who had been in seclusion with another man (Sifrei Devarim 270:10; Yevamot 11b).

[HER FORMER HUSBAND, WHO SENT HER AWAY, MAY NOT TAKE HER AGAIN TO BE HIS WIFE] AFTER THAT SHE IS DEFILED — “this includes a sotah (a suspected adulteress) who had been in seclusion [with a man against whom her husband had warned her not to seclude herself].” This is Rashi’s language. But the meaning thereof is that she had committed adultery while she was a married person, but in the case of a sotah who had merely been secluded and it is not known whether she was defiled — he [her husband] does not transgress this prohibition [if he continues to live with her]. It is so clearly explained in the first chapter of Tractate Yebamoth:³³⁵Yebamoth 11b. “What is the meaning of v’nisterah?³³⁶Numbers 5:13: and it be hid from the eyes of her husband, v’nisterah,’ and she be defiled. She committed adultery. And why does Scripture refer to it as v’nisterah [which means, ‘but she was secluded’]? It is a more seemly expression.” On this answer the Gemara asked: “If she committed adultery — that [aspect] is clearly stated, and she hid and she be defiled,³³⁶Numbers 5:13: and it be hid from the eyes of her husband, v’nisterah,’ and she be defiled. [and therefore v’nisterah in the verse before us must have another meaning]! It is to declare that the husband [whose wife committed adultery and, as a result was divorced] transgresses a negative commandment [if he remarries her].”³³⁷Thus it is proven that this verse applies only if adultery was actually committed, but not if she had just been alone with a man and it is not known whether she was defiled. In the case of mere seclusion, after previously having been warned about it, by her husband, he is forbidden to live with her until she drinks of the waters of bitterness (see Numbers 5:15-28). And if so, Scripture states here: “Her former husband, who sent her away, may not take her again to be his wife ‘and’ after that she is defiled [he may also not take her again].” Thus, these are two negative commandment: he warns against remarrying his own divorcee after she had married [someone else and was divorced or widowed], and he warns against remarrying his [former] wife who had been defiled by adultery [and divorced]. And in line with the plain meaning of Scripture the expression after that she is defiled refers to the first husband, the verse suggesting that because she “knew” [i.e., married] another man she is accounted to him [i.e., the first husband] as “defiled.”
Now these are newly-declared commandments both with respect to divorce and remarriage. And the reason for this prohibition is so that people should not exchange their wives with one another: he would be able to write her a bill of divorce at night, and in the morning she will return to him. This is the sense of the expression, and thou shalt not cause the Land to sin,³³⁸Verse 4 before us. for this is a cause of great sins. And in the Sifre it is stated:³³⁹Sifre, Ki Theitzei 270. “And thou shalt not cause the Land to sin³³⁸Verse 4 before us. — this is intended to admonish the court concerning this.”

כי תועבה היא, because this is a sure recipe leading to legalised adultery, people marrying for short periods of time, and then legally swapping wives by going through phony but legally correct divorce procedures.