תלמוד על כתובות 10:2

HALAKHAH: “If he did not write her “the male children,” etc. That is what Rebbi Immi said, that a man should be disposed to give generously to his daughter²³⁸If he knows that the dowry will remain the possession of his grandchildren, he will be more inclined to provide his daughter with a dowry. In the Babli, 52b, the explanation is ascribed to R. Joḥanan and the recommended amount is 10% of the father’s property.
The same statememt is also in Halakhah 10:2..