Abu Mu'awiyah Amr bin Abdullah bin Wahb al-Nakha'i (may Allah have mercy on him) says: I said to al-Sha'bi (may Allah have mercy on him), or I heard a man say to al-Sha'bi (may Allah have mercy on him): I recognise the engraving of my ring on the deed, but I do not know (recall) the testimony. He said: Do not testify except to what you know, for many people make engravings on rings.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الشهادات / 20588