Musnad Ahmad 25:257

Waki’ narrated to us, Shu’bah narrated to us, from al-Hakam, from Yahya ibn al-Jazzar, from Suhayb, from Ibn Abbas, who said: "The Prophet, peace and blessings of Allah be upon him, was praying, and two young girls from Banu Abd al-Muttalib came until they took hold of his knees, so he separated them."