Sayyiduna Zayd bin Thabit (may Allah be pleased with him) narrates that the Prophet (peace and blessings be upon him) said: "I am leaving among you two things as successors: the Book of Allah, which is a rope extended between the earth and the heaven (the narrator is unsure; perhaps the words are:) a rope extended from the heaven to the earth; and my 'itrah (close kin), my Ahl al-Bayt. These two will not separate from each other until they both come to me at the Pond."
Ahmad recorded it, and its chain is jayyid (good).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب المناقب / 14957