False testimony is another major sin. This is not one of the qualities of a believer. It leads to injustice. It also effaces fairness and equity and poses danger to public safety and security.
Allaah says (interpretation of the meaning):
“…and let him be afraid of Allaah, his Lord. And do not conceal testimony, for whoever conceals it, his heart is indeed sinful…” [Baqarah 2:283]
“So avoid the uncleanliness of idols and avoid false statement.” [Hajj 22:30]
The Messenger of Allaah (peace and blessings of Allaah be upon him): He who appropriated the right of a Muslim by (swearing a false) oath, Allah would make Hell-fire necessary for him and would declare Paradise forbidden for him…” (Muslim)
In another narration, he (peace and blessings of Allaah be upon him) said: “Shall I not tell you of the greatest of major sins?” We said, “Yes indeed, O Messenger of Allaah.” He said, “Associating others with Allaah (shirk) and disobedience towards parents.” He was reclining, but then he sat up and said, “And false speech and false witness, and false speech and false witness,” and he kept on saying it until we (listeners) thought he would never stop. (Al-Bukhari and Muslim)
…Abide by the truth even though your mind deserts you.