Musnad Abu Ya'la al-Mawsili 152:98

Abu Khaythama narrated to us, Jarir narrated to us, from al-A'mash, from Abu Wa'il, from Abdullah: A man came to the Messenger of Allah, may Allah bless him and grant him peace, and said, "O Messenger of Allah, what do you say about a man who loves a people but has not joined them?" The Messenger of Allah, may Allah bless him and grant him peace, said, "A person is with whom he loves."