It was narrated from Jabir that 'Umar bin al-Khattab رضي الله عنه told him that the Messenger of Allah ﷺ saw a man doing wudoo' to pray Zuhr, and he missed a spot the size of a toenail. The Messenger of Allah ﷺ saw him and said:
`Go back and do your wudoo' properly` So he went back and did wudoo', then he prayed.