Reference for Avodah Zarah 73:7

א"ל רבי (אליעזר) [אלעזר] לההוא סבא כי שריתוה לאלתר שריתוה דלא אתי או דלמא לאחר שנים עשר חודש דהא איקיים ליה תנאיה

R. Elazar asked a certain old man: When you permitted a woman [to remarry in the circumstances described above], did you allow her to do so immediately since he is not going to return, or perhaps it was after twelve months since his condition had then been fulfilled?

Jastrow