1,782. A Condition to Marry a Particular Person
Hilchos Geirushin 8:13
If a man divorces his wife on the condition that she marry person Y and she does so, then divorce is effected the same as it would be with any other condition. Nevertheless, the Sages ruled that she shouldn’t marry that man, nor any other. She shouldn’t marry that man out of concern that people will suspect the parties of wife-swapping; she shouldn’t marry anyone else because her get isn’t effective until she meets the condition. If she violates the ruling of the Sages and marries that man, she need not get divorced. If she marries anyone else before marrying person Y, then the get is voided and she must leave the new husband; any offspring from that relationship are illegitimate. The second man, however, must divorce her using a get (for appearances’ sake, so onlookers don’t think a married woman left her husband without one).
Hilchos Geirushin 8:14
If a man tells his wife, “This is your get but the parchment on which it’s written belongs to me,” then divorce is not effected because the marital bond hasn’t been severed. If he divorces her on the condition that she give him the parchment, then divorce is effected if she meets the condition.