It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that my beloved friend (peace and blessings be upon him) advised me regarding three things which I will not leave until my death: (1) to perform Witr prayer before sleeping, (2) to fast three days in every month, (3) not to abandon two rak'ahs of Duha prayer, because this is the prayer of those who turn back (to Allah).