Shama-il Tirmidhi Chapter 012, Hadith Number 001 (090).

'Ali bin Abi Taalib Radiyallahu 'Anhu says: "Rasulullah Sallallahu Alayhi Wasallam wore his ring in the right hand".

Commentary.
Various narrations have been quoted regarding whether Sayyidina Rasulullah Sallallahu'Alayhi Wasallam wore the ring on his right or the left hand. A group of muhadditheen have preferred the view that he wore the ring on his right hand. This is also the view of Imaam Bukhaari, Imaam Tirmidhi, and other muhadditheen.' A few of the 'ulama have concluded that he wore it on the right hand, but sometimes wore it on the left. The 'ulama differ as to which hand it is best to wear a ring. Among the Hanafi 'ulama there are different opinions. A few say it is best to wear it on the left hand and others say both hands are equal. Shaami has quoted both views. Mulla 'Ali Qaari has quoted a saying of the Hanafis, that it is best to wear it on the right hand. According to the madhhab, the view stated by Shaami is more reliable (acceptable). Imaani Nawawi has stated that it is permissible according to the majority of the 'ulama, to wear it on either hand without karaahah. The Maalikis state it is better to wear it on the left hand. In short both are proven from the hadith. The 'ulama have also given preference to both. It is mentioned in Durri Mukhtaar from Qahistani that it has become a symbol of the Rawaafid (Shi'as) to wear a ring on the right hand, therefore it is waajib to abstain from wearing it on the right hand. The author of Durri Mukhtaar says that it is possible that it was the symbol of the Rawaafid at that time and now it is not. Maulana Cangohi writes in his kitaab 'Kaukabi Durri' that because the wearing of the ring on the left hand is the symbol of the Rawaafid, it is makruh to do so. Maulana (Khalil Ahmad) Saharanpuri has given the same view in his 'Badh-lul Majhud' and has also written that although there is a difference of opinion whether the Rawaafid are Muslims or non-Muslims, there is no difference of opinion in that they are faasiqs. It is very important to save one's self from imitating the fussaaq (plural of faasiq). (Now after the Iranian revolution the belief of the Rawaafid (Shi'ah) has been openly propagated and made known. They reject the fundamental beliefs of Islaam and hence are apostates and out of the fold of Islaam).