Musnad Ahmad 26:538

Yahya and Abd al-Rahman narrated to us, from Sufyan, from his father, from Abu al-Duha, from Abdullah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "For every prophet, there are allies among the prophets, and my ally among them is my father, the intimate friend of my Lord, the Almighty and Majestic." Then he recited: "Indeed, the most worthy of Abraham among the people are those who followed him [in his time] and this prophet, and those who believe" [Al Imran: 68].