Sayyiduna Abu Dharr (may Allah be pleased with him) says: I was the fourth in accepting Islam; three men had accepted Islam before me, and I was the fourth. I came to the Messenger of Allah (peace and blessings be upon him) and said: Peace be upon you, O Messenger of Allah; I bear witness that there is no god worthy of worship except Allah, and that Muhammad is His servant and Messenger. I saw joy in the face of the Messenger of Allah (peace and blessings be upon him). Then he (peace and blessings be upon him) said: "Who are you?" I said: I am Jundub, a man of Banu Ghifar. It was as though he (peace and blessings be upon him) (on hearing this) held back, and wished that I were from some tribe other than the one I was from. The reason for this was that I was from a tribe who used to steal the pilgrims' belongings with their hooked sticks.
Hadith Referenceالمعجم الكبير للطبراني / باب الجيم / 1604