It is narrated from Sayyiduna Zayd bin Arqam (may Allah be pleased with him); he said: the Prophet (peace and blessings be upon him) halted (during the journey) on the day of al-Juhfah, then he turned towards the people, praised Allah and extolled Him, and then said: "I do not find any prophet except that his lifespan is half the lifespan of the prophet before him, and soon I will be called and I will answer, so what will you say?" The Companions said: "You have given sincere counsel." He said: "Do you not bear witness that there is no true god except Allah and that Muhammad (peace and blessings be upon him) is His servant and Messenger, and that Paradise is true, the Fire is true, and the resurrection after death is true?" The Companions said: "We bear witness." He (peace and blessings be upon him) raised both his hands and placed them on his chest, then said: "And I bear witness along with you." Then he said: "Are you listening?" The Companions said: "Yes." He said: "Indeed I will precede you to the Pond (Hawd), and you will come to me at the Pond, and its breadth is (the distance) between San'a and Busra; in it are cups of silver as numerous as the stars. So see how you will treat the two weighty things (thaqalayn) after me." A caller called out: "O Messenger of Allah, what are the two weighty things?" He said: "The Book of Allah, one end of which is in the hand of Allah, the Mighty and Majestic, and the other end in your hands, so hold fast to it and you will not go astray; and the other is my family ('itrah, that is, the Ahl al-Bayt). And indeed the Subtle, the All-Aware (Allah) has informed me that the two will never separate until they come to me at the Pond, and I have asked my Lord for this for them both. So do not go ahead of them lest you perish, and do not fall short of them lest you perish, and do not teach them, for they are more knowledgeable than you." Then he (peace and blessings be upon him) took the hand of Sayyiduna Ali (may Allah be pleased with him) and said: "Whoever I have more right over than he has over himself, this one (Ali) is his wali. O Allah, befriend whoever befriends him, and be hostile to whoever is hostile to him."
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 4952