If
a husband told his wife, “This is your Get on condition that your serve
my father,” and the father died, - it is a valid Get. The condition was
based on need, and the need was fulfilled.
If a man told his wife, “This is your Get on condition that you nurse my son for two years,” and the son died, the Get is void. The husband wanted to harass her, and did not succeed. Other
s say that the husband wanted to profit, and that the Get is valid. Practically, we rule stringently, but they should have been more specific!