Nasai

"Raised": Their purpose in mentioning this was to indicate that the Prophet (sallallahu alayhi wa sallam) used to wear the ring on the little finger of his left hand, but numerous other narrations establish that he wore the ring on his right hand, because it is an adornment, and he (sallallahu alayhi wa sallam) preferred the right hand in good matters—especially since his ring bore the name of Allah Ta'ala and his own blessed name. The left hand, on the other hand, is used for istinja (cleaning oneself after relieving oneself) and similar tasks. Are such blessed and sacred names befitting for the hand used for istinja? Certainly not. Yes, it is possible that occasionally the ring was worn on the left hand. In general, however, most tasks are performed with the right hand. The Prophet (sallallahu alayhi wa sallam) wore the ring for the purpose of sealing (documents), and sealing is also an action, so it too should be done with the right hand, and that would only be possible if the ring is on the right hand.