Sayyiduna Salamah bin al-Akwa' (may Allah be pleased with him) said: I pledged allegiance to the Messenger of Allah (peace and blessings be upon him) on the day of al-Hudaybiyah, then I moved aside, and the people began pledging allegiance. He said to me: "Will you not pledge allegiance?" I said: "I have already pledged." He said: "And (pledge) again." (Yazid bin Abi Ubayd said:) I asked him: "On what did you pledge allegiance?" He said: "On death."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قتال أهل البغي / 16559