Maliks Muwatta Book 16, Hadith Number 26.
Section : The Prayer over the Dead in General.
Yahya related to me from Malik from Nafi that Abdullah ibn Umar used to say, “No-one should pray over a dead person unless he is in wudu.”
Yahya said that he heard Malik say, “I have not seen any person of knowledge disapproving of praying over either a child born of adultery or its mother.”