Why did the Prophet (peace be upon him) forbid wearing a ring on the index finger and the one next to it, and what is the wisdom behind that?

The Prophet, may God’s prayers and peace be upon him, forbade men from wearing rings on the index and middle fingers. The Sunnah is for the ring to be on the little finger of the left hand for men, because it is further from being exposed to indignity, and because it does not hinder the hand from working.

As for women, they may wear rings on all fingers of their hands and feet.