Musnad Ahmad 626:4

'Abd al-Razzaq narrated to us, Sufyan informed us, from 'Asim al-Ahwal, from Bakr ibn 'Abd Allah al-Muzani, from al-Mughirah ibn Shu'bah, who said: I came to the Prophet, peace and blessings of Allah be upon him, and mentioned to him a woman I was proposing to. He said: "Go and look at her, for it is more likely to create harmony between you." He said: So I went to a woman from the Ansar and proposed to her parents, and I informed them of the saying of the Messenger of Allah, peace and blessings of Allah be upon him. It was as if they disliked that. He said: The woman heard that while she was in her private quarters, and she said: "If the Messenger of Allah, peace and blessings of Allah be upon him, commanded you to look, then look. Otherwise, I adjure you," as if she considered that a grave matter. He said: So I looked at her, and I married her, and he mentioned her compatibility.