Musnad Ahmad 33:752

Ya'qub narrated to us, my father narrated to us, from Ibn Ishaq, Dawud ibn al-Husayn, the freed slave of 'Amr ibn 'Uthman, narrated to me, from Waqid ibn 'Amr ibn Sa'd ibn Mu'adh, from Jabir ibn 'Abd Allah al-Ansari, who said: I heard the Messenger of Allah, may Allah bless him and grant him peace, say: "If one of you proposes to a woman, and he is able to look at some of what invites him to her, then let him do so."