Narrated 'Aisha (Radi-Allahu 'anha):
The Prophet (Sallallahu 'Alaihi Wa Sallam) was asked, "What deeds are loved most by Allah?" He said, "The most regular constant deeds even though they may be few." He added, "Don't take upon yourselves, except the deeds which are within your ability."
Bukhari Vol. 8 : No. 472