…and fulfil (every) engagement, for (every) engagement will be enquired into (on the Day of Reckoning).
وَلَا تَقْرَبُوا۟ مَالَ ٱلْيَتِيمِ إِلَّا بِٱلَّتِى هِىَ أَحْسَنُ حَتَّىٰ يَبْلُغَ أَشُدَّهُۥ ۚ وَأَوْفُوا۟ بِٱلْعَهْدِ ۖ إِنَّ ٱلْعَهْدَ كَانَ مَسْـُٔولًا
But let your communication be, Yea, yea; Nay, nay: for whatsoever is more than these cometh of evil.
By sincerity in religious practice he obtains proficiency in it; being proficient in it he will act up to his words.
When a man voweth a vow unto the LORD, or sweareth an oath to bind his soul with a bond, he shall not break his word; he shall do according to all that proceedeth out of his mouth.
The Master said, "I do not know how a man without truthfulness is to get on. How can a large carriage be made to go without the cross-bar for yoking the oxen to, or a small carriage without the arrangement for yoking the horses?"