Musannaf Ibn Abi Shayba 3:4444

Abu Mu'awiyah narrated to us, from al-A'mash, from Ibrahim, who said: I mentioned to Sa'id ibn Jubayr the statement of Abdullah regarding the Witr being seven or five, and not less than three. Sa'id said: Ibn Abbas said, "I indeed dislike that there should be three [rak'ahs] as Witr, but rather seven or five."