Sahih Bukhari
Sahih Bukhari Volume 005, Book 057, Hadith Number 108.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 57. Companions of the Prophets
Narated By Ibn Abu Mulaika : Muawiya offered one Rak'a Witr prayer after the 'Isha prayer, and at that time a freed slave of Ibn 'Abbas was present. He (i.e. the slave) went to Ibn 'Abbas (and told him that Muawiya offered one Rak'a Witr prayer). Ibn Abbas said, "Leave him, for he was in the company of Allah's Apostle."