Reference for Gittin 151:9
קשיא דרבי מאיר אדרבי מאיר קשיא דרבנן אדרבנן
A contradiction was raised [from the following]: [If a man said], This is your Get on condition that you look after my father for two years, on condition that you suckle my child for two years, then if the father or the child dies the Get is not valid. This is the view of R. Meir. The Sages, however, say that although the condition has not been fulfilled the Get is valid, since she can say to him, Produce your father and I will wait on him, produce your child and I will suckle it. Now, R. Meir would seem to be in contradiction with himself, and the Rabbis would also seem to be in contradiction with themselves? — Between the two statements of R. Meir there is no contradiction: the former [speaks of] where [the man] did not double his condition, the latter of where he did double it. Between the two statements of the Rabbis there is also no contradiction; for by the 'Sages' here mentioned we understand Rabban Simeon b. Gamaliel, who said that wherever the obstacle does not arise from her side the Get is valid.