Gittin 8:10 - 9:1

הכל משלימין עליו – and even a slave, and even someone who is ineligible to provide testimony on account of sin.

אלא קרוב שהוא ראוי להעיד בעדות אחרת – for he doesn’t have disqualification to give testimony other than for those near. But a slave or a thief cannot. A slave, - perhaps he will come to bring up genealogical connections; and a thief, perhaps he will come to say that he effectuated repentance; but someone related, everyone knows concerning him that he is a relative, and the Halakah is according to Ben Nanas that anyone may complete it. Nevertheless, only one ineligible witness may affix his signature upon it, and all the rest, require that all of them are valid [witnesses].

המגרש...רבי אליעזר מתיר – The reason of Rabbi Eliezer, as is written (concerning the laws of the Kohanim) (Leviticus 21:7): “nor shall they marry one divorced from her husband. [For they are holy to their God].” Even if they were not divorced from other than their husband, since he said to her: You are divorced from me, but you are not permitted to all [other] men, is for she is forbidden to the priesthood. So we see that it is a Jewish bill of divorce, and here she is permitted to any men except from this, she is permitted to others.

וחכמים אוסרים – since they say that the prohibition of the priesthood is different. For the Biblical verse has increased for them (i.e., the priesthood) additional commandments, and even though that the Jewish bill of divorce would make her ineligible to the priesthood, it would not be a Jewish bill of divorce that would permit her to others. And the Halakah is according to the Sages. But the Rabbis did not forbid other than when he said: “You are permitted to all other men other than so-and-so.” The Rabbis admit that it is a Jewish bill of divorce in that it permitted her to all men through the delivery of the Jewish bill of divorce, but that he made a condition with her that she would not marry that particular individual, for it would be like other kinds of conditions in general. But the Rabbis forbade the one who divorces to say: “Behold, this is your Jewish bill of divorce on the condition that you should marry so-and-so,” so that they would not say that they give their wives to one another as gifts. And every condition that a person makes with regard to a Jewish bill of divorce prior to the writing of the Jewish bill of divorce, even though the condition is not written within it, the Jewish bill of divorce is invalid, but after it was given to her in her hand, he can make whatever condition he wishes to make.