God says
Behold, God bids you to deliver all that you have been entrusted with unto those who are entitled thereto, …. Q.4:58
O you who have attained to faith, do not be false to God and the Apostle, and do not knowingly be false to the trust [amanah] that has been reposed to you; and know that your worldly goods and your children are but a trial and a temptation, and that with God there is a tremendous reward.*-- Q.8:27
* Inasmuch as love of worldly goods and a desire to protect one’s family may lead a person to transgression, they are described as fitnah. However, contrary to the New Testament, the Qur’an does not postulate a contempt for worldly attachments as a pre-requisite of righteousness: it only demands man that he should not allow these attachments to deflect him from the pursuit of moral verities.
O you who have attained to faith! Remain conscious of God, and be among those who are true to their word! -- Q.9: 119
…And be true to every promise – for, verily, [on Judgment Day] you will be called to account for every promise which you have made!* -- Q.17:34
* Lit., “every promise shall be asked about” or “investigated”.
Prophet said
1. “…a Muslim has a pledge with God and His Apostle: so (as a Muslim) don’t act treacherously about your pledge with God.”– H: Bukhari. N: Anas.
2. “Signs of a hypocrite are three: when he speaks, speaks falsehood; when he promises, he breaks it; and when he is entrusted, he proves untrustworthy” – H: Bukhari and Muslim. N: Abu Hurairah.