الكافي- ط الاسلامية, volume 1, page 404

Muhammad b. al-Hasan narrated from some of our companions, from Ali b. al-Hakam, from al-Hakam b. Miskin, from a man of Quraysh from the people of Mecca, who said: Sufyan al-Thawri said to me, "Take us to Ja'far b. Muhammad." So I went with him to him, and we found him mounted on his riding animal. Sufyan said to him, "O Abu Abdillah, narrate to us the sermon of the Messenger of God (peace be upon him and his family) in Masjid al-Khayf." He (Ja'far) replied, "Let me go about my errand, for I have mounted. When I return, I will narrate it to you." Sufyan insisted, "I ask you by your kinship to the Messenger of God (peace be upon him and his family) to narrate it to me now." So he dismounted and called for an inkwell and parchment. Then he said, "Write: In the name of God, the Most Gracious, the Most Merciful. The sermon of the Messenger of God (peace be upon him and his family) in Masjid al-Khayf: 'May God brighten the face of a servant who hears my words, retains them, and conveys them to those who did not hear them. O people, let the one who is present convey to the one who is absent. Perhaps a bearer of knowledge is not understanding, and perhaps he conveys it to one who understands better than he does. Three things the heart of a Muslim will never harbor ill against: sincerity in action for God, sincere counsel to the leaders of the Muslims, and adherence to their congregation, for their supplication encompasses those behind them. Believers are brothers, their blood is equal, and they are united against others. The protection given by the lowest among them is binding on all.'" Sufyan wrote it down and read it back to Ja'far, then he mounted again. As we walked along the road, Sufyan stopped and said, "Wait, let me review this hadith." I said to him, "By God, Abu Abdillah has bound something to your neck that will never leave you." He asked, "And what is that?" I said, "Three things: 1. **Sincerity in action for God**—we understand that. 2. **Sincere counsel to the leaders of the Muslims**—who are these leaders that we must advise? Is it Mu'awiya b. Abi Sufyan, Yazid b. Mu'awiya, Marwan b. al-Hakam, and all those whose testimony we do not accept and behind whom we do not pray? 3. **Adherence to their congregation**—which congregation? Is it the Murji'ah, who claim that even if one does not pray, fast, purify himself from impurity, demolishes the Kaaba, and commits incest with his mother, he still has the faith of Jibril and Mikail? Or is it the Qadariyya, who say that God's will does not prevail but that of Iblis does? Or is it the Haruriyya, who dissociate from Ali b. Abi Talib and accuse him of disbelief? Or the Jahmiyya, who claim that faith is merely the knowledge of God and nothing more?" Sufyan exclaimed, "Woe to you! Then who do they say the true leader is?" I replied, "They say, by God, that Ali b. Abi Talib is the Imam whose counsel is obligatory upon us, and that adherence to the congregation means his household." At that, Sufyan took the paper, tore it up, and said, "Do not tell anyone about this!"

Translation: Muhammad Sarwar — attributed by Thaqalayn·The Arabic above is the original.