Mukhtasar Muslim

Ameer-ul-Mu'mineen Sayyiduna Ali (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) forbade me from wearing a ring on this finger or this finger, and he pointed towards the middle finger and the one next to it. (Because these fingers are involved in every task and the ring would cause inconvenience, whereas the little finger remains separate, so it is better to wear the ring on it.)