Shulchan Arukh Even HaEzer · Siman 147

English

How does a man divorce on a condition? It is not that he says: Write a get for my wife on this condition, or write and give it to her on this condition, and there is no need to say that he should not write in the get: On this condition so-and-so divorces so-and-so, rather how does he do it? He tells the scribe to write and the witnesses to sign, and they write a valid get without any condition at all. And afterwards he gives her the get and says to her: Behold this is your get or behold you are divorced from me on such and such condition, or he says to them or to an emissary: Give her this get on such and such condition.

English

[If] he wrote the stipulation in the bill [of divorce] after he finished writing the personalized part of the bill, it is valid, whether he wrote it before the witnesses' signing or he wrote it after the witnesses' signing. However, if he wrote it before the personalized part of the bill [of divorce], even if he wrote "on condition that such-and-such", this is a possible divorce, for a claim to the body of the bill [of divorce] remains his. Likewise, if he stipulated orally before the writing of the personalized part, this is a possible divorce.

English

Whoever divorces on a stipulation that annuls the bill [of divorce] -- such as that he stipulated to her that she shall not eat meat and not drink wine all the days of her life, or that she shall be permitted to any man except So-and-so, or that he stipulated other stipulations before the writing of the personalized part [of the bill of divorce] -- if the stipulation was written in the bill [of divorce] and he thereafter erased it and gave [the bill] to her, she is possibly divorced. If, [however,] the stipulation was oral, he takes the bill from her and thereafter gives it to her without a stipulation at all or with a valid stipulation.