Malik related to me that Abd ar-Rahman ibn al-Qasim heard hisfather al-Qasim ibn Muhammad say, "I have prayed witr after dawn."Malik said, "Only a person who oversleeps so that he does notdo the witr prays it after dawn. No one should intentionally make hiswitr after dawn."
App reference: Book 7, Hadith 28
USC-MSA web (English) reference: Book 7, Hadith 28
Arabic reference: Book 7, Hadith 282