Sahih Muslim , Book 6, Hadith 256 (In-Book) ⓘ
'A'isha is reported to have said that the Messenger of Allah was asked about the act most pleasing to Allah. He replied: That which is done continuously, even if it is small.
حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، حَدَّثَنَا شُعْبَةُ، عَنْ سَعْدِ بْنِ إِبْرَاهِيمَ، أَنَّهُ سَمِعَ أَبَا سَلَمَةَ، يُحَدِّثُ عَنْ عَائِشَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم سُئِلَ أَىُّ الْعَمَلِ أَحَبُّ إِلَى اللَّهِ قَالَ " أَدْوَمُهُ وَإِنْ قَلَّ " .
also referenced under: Hadith 782 (Reference) & Book 4, Hadith 1711 (USC-MSA)