Reference for Gittin 150:5

ולימא לא יהא גט אם לא מתי בעינן תנאי קודם למעשה

— A man does not like to commence with a mention of evil for himself. But why should he not say, This will not be a Get if I do not die?<span class="x" onmousemove="('comment',' Why did Samuel insist on the exact words of the formula? ');">⁵</span>

Jastrow