Musnad Ahmad 1153:1216

Husayn ibn Ali narrated to us, from Za'idah, from Mughirah, from al-Sha'bi, who said: Aisha said: "It is not appropriate for anyone to hate Usamah after what I heard the Messenger of Allah, peace and blessings of Allah be upon him, say: 'Whoever loves Allah the Almighty and His Messenger, let him love Usamah.'"