I went along with Husain bin Sabrah and 'Amr bin Muslim to Zaid bin Arqam (May Allah be pleased with them) and, as we sat by his side, Husain said to him, "Zaid, you acquired great merits, you saw Messenger of Allah (ﷺ), listened to him talking, fought by his side in (different) battles, and offered Salat (prayer) behind him. Zaid, you have indeed earned great merits. Could you narrate to us what you heard from Messenger of Allah (ﷺ)?" Zaid said, "By Allah! I have grown old and have almost spent up my age and I have forgotten some of the things which I remembered in connection with Messenger of Allah (ﷺ), so accept what I narrate to you, do not compel me to narrate what I fail to narrate". He then said, "One day Messenger of Allah (ﷺ) stood up to deliver a Khutbah at a watering place known as Khumm between Makkah and Al-Madinah. He praised Allah, extolled Him, and exhorted (us) and said, 'Amma Ba'du. O people, I am a human being. I am about to receive a messenger (the angel of death) from my Rubb and I will respond to Allah's Call, but I am leaving with you two weighty things: the first is the Book of Allah, in which there is right guidance and light, so hold fast to the Book of Allah and adhere to it.' He exhorted (us to hold fast) to the Book of Allah and then said, 'The second is the members of my household, I remind you (to be kind) to the members of my family. I remind you (to be kind) to the members of my family. Husain said to Zaid, "Who are the members of his household, O Zaid? Aren't his wives the members of his family?" Thereupon Zaid said, "His wives are the members of his family. (But here) the members of his family are those for whom Zakat is forbidden". He asked, "Who are they?" Zaid said, "Ali and the offspring of 'Ali, 'Aqil and the offspring of 'Aqil and the offspring of Ja'far and the offspring of 'Abbas." Husain asked, "For all of them the acceptance of Zakat is forbidden?" Zaid (May Allah be pleased with him) said, "Yes".

[Muslim].

Another narration is: Messenger of Allah (ﷺ) said, "I am leaving behind me two weighty things. One of them is the Book of Allah; that is the strong rope of Allah. Whosoever holds firmly to it, will be the guided, and whosoever leaves it goes astray".