It is narrated from Sayyidah Umm Salamah (may Allah be pleased with her) that she said: "By the One who took his (peace and blessings be upon him) soul" (meaning the Prophet (peace and blessings be upon him)), "he (peace and blessings be upon him) did not pass away until most of his prayer, except the obligatory prayer, was performed sitting; and the deed most pleasing to him (peace and blessings be upon him) was the one that its doer keeps up constantly, even if it is little."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 19817