Reference for Gittin 35:9

איתמר מאימתי כתובה משמטת

because the husband has not been alone with her in the interval. It has been taught in accordance with Samuel: If a man entrusts to a third party a Get for his wife, and says to him, 'Do not give it to her till three months have passed', she is at liberty to marry from the moment he has given it to her, nor do we concern ourselves lest it should have become an 'old Get', since he has not been alone with her in the interval.

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