Musnad Ahmad 792:22

Yahya ibn Sa'id narrated to us, from Bahz, who said: My father informed me, from my grandfather, who said: I came to the Messenger of Allah (peace and blessings of Allah be upon him) and said: "O Messenger of Allah, by Allah, I did not come to you until I had sworn more times than the number of these"—and he struck one of his hands against the other—"that I would not come to you, nor would I come to your religion. And I have come as a man who knows nothing except what Allah and His Messenger have taught me. I ask you by the Face of Allah, for what did our Lord send you to us?" He said: "With Islam." I said: "O Messenger of Allah, and what is the sign of Islam?" He said: "That you say: 'I have submitted my face to Allah and detached myself,' and that you establish prayer, and give zakat. Every Muslim is forbidden to another Muslim; they are two brothers who support one another. Allah does not accept from a polytheist who associates partners with Him after he has accepted Islam any deed, until he separates from the polytheists to the Muslims. What is the matter with me holding you by your waistbands away from the Fire? Behold, my Lord is calling me, and He will ask me: 'Have you conveyed [the message] to My servants?' And I will say to Him: 'My Lord, I have indeed conveyed it to them.' So let the witness among you convey it to the absent." "Then you will be summoned, and your mouths will be sealed with the *fidam* (a covering). And the first thing that will speak—" and he said in Wasit: "will testify"—and he said: "And the Messenger of Allah (peace and blessings of Allah be upon him) struck his hand upon his thigh." I said: "O Messenger of Allah, is this our religion?" He said: "This is your religion, and wherever you do good, it will suffice you."