Abd al-Rahman bin Abi Bakrah narrates from his father (Sayyiduna Abu Bakrah, may Allah be pleased with him) that we were with the Messenger of Allah (peace and blessings be upon him), and he (peace and blessings be upon him) said: "Shall I not tell you about the greatest of the major sins? (1) Associating partners with Allah, (2) disobedience to parents." He (peace and blessings be upon him) was reclining; then he sat up straight and said: "(3) False testimony, false testimony, false testimony," or (he said): "false speech." He (peace and blessings be upon him) kept repeating it until we said: If only he (peace and blessings be upon him) would fall silent.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الشهادات / 20578