What is the event that occurred when the Prophet Muhammad (saw) offered five rak'at in Zuhr prayer?
 Narrated `Abdullah:                     "Once the Prophet offered five rak`at in Zuhr prayer. He was asked, "Is there an increase in the prayer?" The Prophet said, "And what is it?" They said, "You have prayed five rak`at.' So he bent his legs and performed two prostrations (of Sahu).