Hazrat Hammaad bin Salamah says that he saw Hazrat Abdur Rahman bin Abi Rafe' wearing a ring on his right hand. He asked him the reason and he replied, "I had seen Hazrat Abdullah bin Ja'far radiyallahu anhu wearing a ring on his right hand, and he said that he had seen the Prophet of Allah sallallahu alaihe wasallam wear a ring on the right hand."
English reference: Book 12, Hadith 91
Arabic reference: Book 13, Hadith 97