The messenger of Allah (PBUH&HF) said: "I am leaving for you two precious and weighty Symbols that if you adhere to BOTH of them you shall not go astray after me. They are, the Book of Allah, and my progeny, that is my Ahlul-Bayt. The Merciful has informed me that These two shall not separate from each other till they come to me by the Pool (of Paradise)."
Sunni references:
Sahih al-Tirmidhi, v5, pp 662-663,328, report of 30+ companions, with reference to several chains of transmitters.
al-Mustadrak, by al-Hakim, Chapter of "Understanding (the virtues) of Companions, v3, pp 109,110,148,533 who wrote this tradition is authentic (Sahih) based on the criteria of the two Shaikhs (al-Bukhari and Muslim).
Sunan, by Daarami, v2, p432
Musnad, by Ahmad Ibn Hanbal, v3, pp 14,17,26,59, v4, pp 366,370-372, v5, pp 182,189,350,366,419
Fadha'il al-Sahaba, by Ahmad Ibn Hanbal, v2, p585, Tradition #990
al-Khasa'is, by al-Nisa'i, pp 21,30
al-Sawa'iq al-Muhriqah, by Ibn Hajar Haythami, Ch. 11, section 1, p230
al-Kabir, by al-Tabarani, v3, pp 62-63,137
Kanz al-Ummal, by al-Muttaqi al-Hindi, Chapter al-Iti'sam bi Habl Allah, v1, p44.
Tafsir Ibn Kathir (complete version), v4, p113, under commentary of verse 42:23 of Quran (four traditions)
al-Tabaqat al-Kubra, by Ibn Sa'd, v2, p194, Pub. by Dar Isadder, Lebanon.
al-Jami' al-Saghir, by al-Suyuti, v1, p353, and also in v2
Majma' al-Zawa'id, al-Haythami, v9, p163
al-Fateh al-Kabir, al-Binhani, v1, p451
Usdul Ghabah fi Ma'rifat al-Sahaba, Ibn al-Athir, v2, p12
Jami' al-Usul, Ibn al-Athir, v1, p187
History of Ibn Asakir, v5, p436
al-Taj al-Jami' Lil Usul, v3, p308
al-Durr al-Manthoor, al-Hafidh al-Suyuti, v2, p60
Yanabi al-Mawaddah, al-Qundoozi al-Hanafi, pp 38,183
Abaqat al-Anwar, v1, p16