Tractate Gittin - Chapter 6 - Mishnah 6 גיטין פרק ו׳ משנה ו׳

If a man had been thrown into a pit and cried out, “Whoever hears his voice should write a get for his wife”, those who hear should write a get and give it to her. If a healthy man says, “Write a get for my wife”, his intention is merely to play with her. It once happened that a man in good health said, “Write a get for my wife”, and then went up on to a roof and fell and died, and Rabban Shimon ben Gamaliel said that the Sages said: if he had thrown himself down this is a get, but if the wind had blown him over it was not a get.