Harun bin Abdullah (may Allah have mercy on him) said: "Sayyiduna Aslam (may Allah be pleased with him), the freed slave of the Messenger of Allah (peace and blessings be upon him), died after the martyrdom of Sayyiduna Uthman (may Allah be pleased with him), in the year 35 AH."
Hadith Referenceالمعجم الكبير للطبراني / باب الألف / 906