1,718. A Get Must Be Written for a Particular Man and a Particular Woman

Hilchos Geirushin 3:1

If a get wasn’t written specifically for the man who is divorcing and the woman who is being divorced, then it is invalid. Therefore, let’s say that a scribe was writing a get for practice or to teach his students. A man came along and saw that this get included his name, his wife's name and the name of his city, so he took it and used it to divorce his wife. In such a case, divorce is not effected.

Hilchos Geirushin 3:2

Not only that, let’s say that a man had a get written so that he could divorce his wife but he changed his mind. Another resident of the city found it and saw that he and his wife had the same names as the couple for whom the get had been written. If this second man takes the get and uses it to divorce his wife, divorce is not effected even though this get was written for the purpose of divorce.