Sahih Muslim Book 6, Hadith Number 2547.

Chapter : Abrogation of the words of Allah: “And as for those who can fast (but do not) the expiation is” by the words: “Whosoever witnesses it he shall have to fast the whole month” (ii. 184).

Salama b. Akwa’ (Allah be pleased with him) reported that when this verse was revealed: “And as for those who can fast (but do not) expiation is the feeding of a needy person” (ii. 183), (he who liked to observe fast did observe it) and he who felt reluctant to observe it ate and expiated till the verse was revealed which abrogated it.