Yahya related to me from Malik from Nafi that Salim ibn 'Abdullah
said, "I was with Abdullah ibn Umar on a journey and after the sun had
risen I saw him do wudu and then pray. So I said to him, 'This isn't a
prayer that you normally do. 'He said, 'After I had done wudu for the
subh prayer, I touched my genitals. Then I forgot to do wudu. So I did
wudu again and repeated my prayer.' "
Muwatta Malik Book 2, Hadith 64