Musnad Ahmad 5:545

Waki' narrated to us, Hisham bin 'Urwah narrated to us, from his father, from 'Abdullah bin Ja'far, from 'Ali, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The best of its women is Khadijah, and the best of its women is Maryam bint 'Imran."