The Prophet Mohammad (SW) said, The messenger of my God is about to come to me and I shall answer (meaning death is close and the angel Izrael is coming)I am leaving with you the two weighty things:
The first is the Book of Allah , in which you find guidance and enlightenment, and the second is my household.I remind you, by Allah,of the people of my household...

Sunni References:

Sahih Muslim, chapter of the virtues of Imam Ali (AS), vol.V,p.122? Sahih al-Tirmithi,vol.V,p.328? Mustadrak al-Hakim, vol.III, p.148? Musnad Ahmad ibn Hanbal , vol.III, p.17.