Musnad Ahmad 20:6

Yazid narrated to us, Hammad ibn Salamah informed us, he said: I saw Ibn Abi Rafi' wearing a ring on his right hand, so I asked him about that. He mentioned that he saw Abdullah ibn Ja'far wearing a ring on his right hand. And Abdullah ibn Ja'far said: "The Messenger of Allah, may Allah bless him and grant him peace, used to wear a ring on his right hand."