The Cattle - 6:152 Do not approach the property of orphans until they reach the age of maturity. Measure and weigh accurately. We do not burden a person with what he is not able. When you speak, be truthful even against your relatives. Keep your promise to Allah. These are His admonitions to you that you may take a lesson.
The importance of a promise to Allah:
The Coalition/33:15 They had promised Allah before that they would not turn their backs and flee. Every promise made to Allah will be questioned.

The Bee/16:91 When you make a covenant, fulfill the covenant of Allah. Do not break the oaths which you have strengthened. You had made Allah your surety. Allah knows what you do.

Prophet Joseph/12:66 "I will not send him with you unless you give me a firm promise by Allah that you will bring him to me unless you are all surrounded and prevented. When they promised him, he said: "Allah is witness to what we say"."

The Night Journey/17:34 Do not touch the property of orphans until they reach the age of maturity, except for their benefit. And fulfill your promises. For you will be held accountable for what you have promised.

The Family Of Imran/3:77 Those who exchange their pledge to Allah and their oaths for a small price have no share in the Hereafter. Allah will not speak to them, nor will He look upon them on the Day of Resurrection, nor will He purify them. For them is a painful torment.
The Family Of Imran/3:187 "Allah had taken a promise from those to whom the Book was given, saying, "You will certainly make it clear to the people and you will not conceal it."But they threw it behind their backs and sold it for a small price. What an evil exchange!"

The Women/4:154 "We raised Mount Sinai above them, and We said to them, "Enter humbly through the gate."We said to them, "Do not transgress the prohibition of Saturday"; and We took from them a firm promise."
The Women/4:155 "Allah sealed their understanding because of their breaking their word, because they disbelieved in the signs and proofs of Allah, because they killed the prophets unjustly, and because they said: "We are fixed-minded", yes, because of their disbelief. Therefore few of them believe."

The Table Spread/5:14 "We also took a promise from those who said, "We are Christians,"but they too forgot some of what they were warned about. So We put enmity and hatred between them until the Day of Resurrection. Allah will inform them of all that they did."

The Cattle/6:152 Do not approach the property of orphans until they reach the age of maturity. Measure and weigh accurately. We do not burden a person with what he is not able. When you speak, be truthful even against your relatives. Keep your promise to Allah. These are His admonitions to you that you may take a lesson.

The Heights/7:169 "They were replaced by other generations who inherited the Book. But they said, "We shall be forgiven anyway,"and chose vile and transitory benefits. If similar temporary benefits came to them, they would still choose them. Was not a promise taken from them that they would adhere to the Book and speak only the truth about Allah? Have they not read and learned it? Better for the righteous is the abode of the Hereafter. Do you not understand?"

The Repentance/9:75 "Some of them even promised Allah, "If He grants us out of His bounty, we will spend our money for charity and we will be of the righteous people."
The Repentance/9:76 But when He gave them out of His bounty, they became stingy and turned away.
The Repentance/9:77 Because they broke their promise to Allah and lied, He put hypocrisy in their hearts until the Day when they will meet Him.

The Thunder/13:25 Those who break their covenant after their promise to Allah, those who do not unite what Allah has commanded to be united, and those who make mischief in the earth have deserved the curse and for them is an evil consequence.

Ta-Ha/20:85 "He said, "We tested your people after you, and Samiri led them astray."
Ta-Ha/20:86 "Moses returned to his people, angry and disappointed, and said, "My people, did not your Lord give you a good promise? Could you not wait? Or did you break your covenant with me in order to incur the wrath of your Lord?"

The Coalition/33:22 "When the believers see the parties (ready to attack), they say, "This is what Allah and His messenger promised us. Allah and His messenger have spoken the truth."This (dangerous situation) only strengthened their faith and submission."
The Coalition/33:23 There are such of the believers who have fulfilled their promise to Allah. Some of them fulfilled their pledge (became martyrs) and some of them are waiting. They have never wavered.
The Coalition/33:24 Thus Allah rewards the truthful with their truthfulness. And He punishes the hypocrites if He wills, or accepts their repentance. Allah is Forgiving, Merciful.

Yaseen/36:60 O children of Adam, did I not take a promise from you that you would not serve Satan? He is your open enemy.
Yaseen/36:61 Serve Me. This is the most right way.
Yaseen/36:62 Yet he has led astray many generations from you. Would you never use your reason?
Yaseen/36:63 This is Hell, which is promised to you!
Yaseen/36:64 Burn therein as a consequence of your disbelief.

The Victory/48:10 Those who pledge allegiance to you have pledged allegiance to Allah. Allah´s hand is upon their hands. Whoever breaks his pledge breaks it against himself. And whoever fulfills his promise to Allah, We shall give him a great reward.

The Family Of Imran/3:81 "Allah had taken a covenant from the Prophets saying: "I will give you the Book and wisdom, then when a messenger comes to you who confirms what is with you, you will believe in him and support him. Have you accepted this and have you promised to fulfill this covenant?"When they said, "We accept,"he said, "Then bear witness, and I am one of those who bear witness with you."

The Coalition/33:7 We took a covenant (promise) from the Prophets: from you, Noah, Abraham, Moses and Jesus son of Mary. We had taken from them a firm promise.
The Coalition/33:8 So We will ask the righteous about their righteousness. And for the disbelievers a painful torment has been prepared.