It is narrated from Sayyiduna Zayd bin Arqam (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "I am leaving among you two weighty trusts: the Book of Allah and my 'Itrah, that is, my Ahl al-Bayt (household), and these two will never separate until they come to me at the Pond (al-Hawd)."
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 4961