Silsilat al-Ahadith al-Sahihah

Salim bin Amir says that I heard Sayyiduna Abu Bakr (may Allah be pleased with him) say that the Messenger of Allah (peace and blessings be upon him) said: "Go out and announce among the people that whoever testifies that Allah alone is worthy of worship, Paradise will become obligatory for him." He says: I went out to make the announcement, and I encountered Sayyiduna Umar bin Khattab (may Allah be pleased with him). He said: Abu Bakr, where and how? I said: The Messenger of Allah (peace and blessings be upon him) ordered me to go and announce among the people that whoever testifies that there is no deity worthy of worship except Allah, Paradise will become obligatory for him. Sayyiduna Umar (may Allah be pleased with him) said: (Without making this announcement) return to the Messenger of Allah (peace and blessings be upon him); I fear that people will rely on this (glad tidings) and abandon action. I returned, and the Prophet (peace and blessings be upon him) asked: "Why have you come back?" I told him what Sayyiduna Umar had said. He said: "Umar has spoken the truth."