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 the true deity, Paradise will become obligatory for him." He says: I went out to make the announcement, and ahead 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) has commanded me to go and announce among the people that whoever testifies that there is no one 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 (good news) and abandon acting (righteously). I returned, and the Prophet (peace and blessings be upon him) asked: "Why have you come back?" I told him what Sayyiduna Umar (may Allah be pleased with him) had said. The Prophet (peace and blessings be upon him) said: "Umar has spoken the truth."