Matthew 1.19 reads, jIwshVf deV oJ ajnhVr aujth'", divkaio" w]n kaiV mhV qevlwn aujthVn deigmativsai, ejboulhvqh lavqra/ ajpolu'sai aujthvn. Several questions come to mind as one reads this verse, some of which the Mishnah may help to answer.
First, the text says that Joseph desired (ejboulhvqh) to divorce Mary secretly. Had Joseph gone through with delivering the bill of divorce, could it be retracted? Was there a point of no return, a point in which the divorce proceedings could not be nullified?
In answer to these questions, the Mishnah has much relevant material. First, Gittin 1.6, 4.1, and 6.1 point out that before a bill of divorce was handed to the wife it could be retracted, even though this be after a man charged a messenger (though not a slave) to deliver the bill. Of the three texts, Gittin 4.1 clarifies this best:
If one sends a letter of divorce to his wife, and he overtakes the messenger or dispatches another messenger after him, and says to him [i.e., to the first messenger], “The letter of divorce which I gave you is canceled [or abolished, suspended],” then it is canceled. If he reaches his wife first, or if he sends another messenger to her, and he says to her, “The letter of divorce which I sent to you is canceled,” then it is canceled. [But] if [news of cancelation arrives] after [the letter of divorce] comes into her hands, it is not possible for him to cancel it.
Thus, in the case of Joseph and Mary, once she would receive such a letter, the divorce could not be retractable.
A related question, however, is whether the husband could remarry his wife after the divorce. Gittin 4.7 is the most enlightening Mishnah on this question in relation to Matt 1.19: “If one divorces his wife because of her evil name [i.e., due to adultery], he may not retract [the divorce].” Thus, if this applies to women betrothed as well as fully married women, then Joseph would never be allowed to marry Mary had he gone through with the divorce. (Sanhedrin 7.9 suggests that one who had intercourse with a betrothed virgin [hlwtb] who was still living at home, would be stoned. The text, however, does not mention the fate of the betrothed girl.)
Second, the text says that Joseph desired to divorce Mary secretly (lavqra/). How secret could this be? Was it possible for only Joseph and Mary to know? Several Mishnayoth help to answer this question. First, Kethuboth 4.4 declares, “The father has authority over his daughter regarding her betrothal… and he receives her bill of divorce.” However, Gittin 6.2 both clarifies and confuses this picture: “If a girl [hrun] is betrothed, she or her father receives the letter of divorce.” Here hrun rather than tb is used to describe the girl. Jastrow suggests that hrun referred to a girl “between twelve and twelve and a half years of age” (2.922). Thus it might not apply to Mary (although Matthew does not record her age at the time of betrothal). Also, what seemed to confuse the picture more is that Kethuboth 4.4 states that the father is to receive the bill, while Gittin 6.2 suggests that such is optional rather than mandatory (though Rabbi Judah had a dissenting opinion, agreeing with Kethuboth 4.4). Thus we cannot dogmatically say that Joseph must have sent the divorce papers to Mary’s father.
Did anyone else have to know? Gittin 8.10 and 9.4 answer that question. Gittin 8.10 says, “And what is considered a deficient [literally, ‘bald’] letter of divorce? Any such whose folds outnumber its witnesses.” Gittin 9.4 is more to the point:
Three [kinds of] letters of divorce are invalid… If one wrote in his own handwriting but there are no witnesses to it, one that had witnesses to it but had no date on it, one which had a date on it but there was affixed only [the signature of] one witness.
A modification of this is offered by Rabbi Eliezer: “Even though there be no [signatures of] witnesses on it, but he [i.e., the husband] had delivered it to her in the presence of witnesses, it is valid [rvk].” In either case, at least two witnesses were needed at some point in order to make the divorce papers legal and binding.
Therefore, although Joseph desired to divorce Mary secretly, he had to at least let two others in on the secret and possibly even Mary’s father.
In summary, had Joseph sent a bill of divorce to Mary it could not be retracted once it reached her because, as far as was evident to him, she had committed an immoral act. And although he desired to divorce her secretly, at least two other people had to know about the matter. But since he only desired to do this and did not actually go through with the act, her dignity was preserved intact.