Signet-rings - Section 2 Mishkat al-Masabih 4393
Arabic hadith text
وَعَنِ ابْنِ عُمَرَ قَالَ: كَانَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يتختم فِي يسَاره. رَوَاهُ أَبُو دَاوُد
Translation
Ibn ‘Umar said the Prophet used to wear a signet-ring on his left hand.Abu Dawud transmitted it.