It is narrated from Sayyiduna Khuraym bin Fatik al-Asadi (may Allah be pleased with him); he said: The Messenger of Allah (peace and blessings be upon him) led the morning prayer, and when he finished (the prayer) and stood up, he said three times: "False testimony is equal to associating partners with Allah." Then he recited this verse: "And shun false speech, being upright for Allah, not associating anything with Him" [Surah al-Hajj: 31].
Hadith Referenceالمعجم الكبير للطبراني / باب الخاء / 4147