Silsilat al-Ahadith al-Sahihah

It is narrated from Sayyiduna Ali (may Allah be pleased with him), he says: When I took possession of the weapons of the Messenger of Allah (peace and blessings of Allah be upon him), I found a piece of paper in the sword of the Messenger of Allah (peace and blessings of Allah be upon him), in which it was written: "Maintain ties with the one who severs relations with you, treat well the one who treats you badly, and speak the truth even if it is against yourself."