The Quran
“And do not mix the truth with falsehood or conceal the truth while you know [it].” [Qur’an; 2:42]
“Woe unto those who give short measure, those who, when they are to receive their due from people, demand that it be given in full but when they have to measure or weigh whatever they owe to others, give less than what is due. Do they not know that they are bound to be raised from the dead (and called to account) on an awesome Day, the Day when all men shall stand before the Sustainer of all the worlds?” [Qur’an; 83:1-6]
Hadith
Narrated `Abdullah: The Prophet (peace be upon him) said, “Truthfulness leads to righteousness, and righteousness leads to Paradise. And a man keeps on telling the truth until he becomes a truthful person. Falsehood leads to Al-Fajur (i.e. wickedness, evil-doing), and Al-Fajur (wickedness) leads to the (Hell) Fire, and a man may keep on telling lies till he is written before Allah, a liar.” [Sahih Bukhari]
Narrated Hudhaifa: Allah’s Messenger (peace be upon him) said to us, “Honesty descended from the Heavens and settled in the roots of the hearts of men (faithful believers), and then the Qur’an was revealed and the people read the Qur’an, (and learnt it from it) and also learnt it from the Sunna.” Both Qur’an and Sunna strengthened their (the faithful believers’) honesty. [Sahih Bukhari]
“Verily Allah does not look to your bodies nor to your faces but He looks to your hearts.” [Muslim]
“He is not one of us who cheats.” [Ibn Majah]
Wabisah bin Ma’bad (may Allah be pleased with him) reported: I went to Messenger of Allah (peace and blessings of Allah be upon him) and he asked me, “Have you come to inquire about piety?” I replied in the affirmative. Then he (peace and blessings of Allah be upon him) said, “Ask your heart regarding it. Piety is that which contents the soul and comforts the heart, and sin is that which causes doubts and perturbs the heart, even if people pronounce it lawful and give you verdicts on such matters again and again.” [Ahmad and Ad- Darmi]
Ibn Al-Qayyim (may Allah have mercy on him) says:
“When falsehood proceeds from the heart to the tongue, it spoils it, and then it goes to the body, and spoils the good deeds, just like it spoiled the words of the tongue. Then falsehood prevails in his words, deeds, and state. Therefore corruption would become firmly embedded in him and its disease would extend to a state of destruction if Allah the Almighty does not cure him with the remedy of truthfulness which cuts off evil at its source.”
Further Information