Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) said: The Prophet (peace and blessings be upon him) said: "O people, I am leaving among you two things which, if you hold fast to them, you will never go astray after me, one of them greater than the other: the Book of Allah, a rope stretched between the heaven and the earth, and my 'itrah (kin), my household. And these two will never separate until they come to me at the Pool."
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 2665