It is narrated from Hazrat Anas (may Allah be pleased with him) that the Prophet (peace and blessings be upon him), while mentioning the major sins, said: They are these—associating partners with Allah, unjustly killing, disobedience to parents. And he said: Shall I not tell you the greatest of the major sins? That is false speech or false testimony.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 12336