Gittin, Chapter 6, Mishnah 6. The Mishnah continues to discuss cases in which the husband does not give complete instructions for the writing and delivery of the get, because of the circumstances he finds himself in.
"Mi shehayah mushlach labor" - One who was thrown into a pit:
The Mishnah opens: "Mi shehayah mushlach labor v'amar: kol hashomea es kolo yichtov get l'ishto - harei eilu yichtevu v'yitenu" - one who was thrown into a pit and said, "Whoever hears my voice should write a get for my wife" - they should write it and give it. This is a person who was thrown into a pit and is in mortal danger there, with no way to get him out. He announces that whoever hears his voice should write a get for his wife, but he does not say to give the get - and nevertheless they write it and give it.
The Gemara explains that even though those who hear him do not know the man and cannot identify him, he listed for them his name and his wife's name, his city and her city, and all the other necessary details. And although he did not explicitly say "give it," since this is a situation of danger and we are concerned that he will die in the pit, we assume that he intended the giving of the get as well.
A healthy man who said "Write a get for my wife":
By contrast, a healthy man - someone who is not in a situation of danger - who said "kisvu get l'ishti" - "write a get for my wife" - and did not say to give it, this assessment of his intent does not apply. It is possible that he only wanted to toy with her, to make things difficult for her and to provoke her, and there is no proof from his words that he wishes to divorce her; perhaps he only wanted the get to be ready and available to him.
As the Gemara explains, several words are missing here in the Mishnah, and at this point it should really have said: "im hochiach sofo al techilaso" - if what happens in the end demonstrates what his true intent was at the outset, then it is a valid get. To illustrate this idea, the Mishnah brings an incident that occurred.
The incident of the healthy man who fell from the roof:
There was an incident with a healthy man who said, "Write a get for my wife," and did not say, "Give it to her." In the meantime they went and wrote the get and gave it to her, and he went up to the top of the roof, fell and died.
Rabban Shimon ben Gamliel said: The Sages said - everything depends on the manner of the fall:
"Im hu atzmo nafal" - if he threw himself off the roof deliberately, that is, he took his own life - it is a valid get. The get is valid provided that it was given while he was still alive, since he must be alive for the get to take effect. Given that the get was delivered while he was still alive, we assume that even beforehand he was in a confused state of mind, and therefore he genuinely wanted her to be divorced - so that she would not become subject to yibum, or for other reasons - and on that basis we assume that he meant to say "give it" as well, even though he did not say so explicitly.
If the wind blew him off - if he fell from the roof by accident, unintentionally, and it never entered his mind that he was about to die - it is not a valid get. For he was not necessarily in a confused state of mind; he was a healthy man, and an accident befell him afterward. And since he did not say "give it" but only "write it," and when a healthy man instructs that a get be written - it may not be given on the strength of that statement alone.
In summary: In this Mishnah we learned the distinction between a man thrown into a pit, where because of his danger we assess that his intent included the giving of the get, and a healthy man who said only "write it," whose intent to divorce we do not assess - unless the end demonstrates what his intent was at the outset, as in the incident of the man who fell from the roof: if he threw himself off deliberately, it is a valid get; if the wind pushed him off, it is not a valid get.