Sahih Muslim | Book 6 | Chapter 24

Narrated by Salama b. Akwa' (Allah be pleased with him)
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.

Narrated by Salama b. Akwa'
Salama b. Akwa' reported: We, during the lifetime of the Messenger of Allah (may peace be upon him), in one month of Ramadan (observed fast according to our liking). He who wished to fast lasted and he who wished to break broke it and fed a needy person as an expiation 1544 till this verse was revealed: "He who witnesses among you the month (of Ramadan) he should observe fast during it" (ii. 184).