Moses Fasts for Forty Days
The days of restless wandering began. Each day ended where it began and began where it ended. They started walking to no destination, day and night, morning and evening. They entered Sinai. Moses came to the same place where he had spoken to Allah for the first time. He appealed to Allah for guidance in judging over his people. Allah instructed him to purify himself by fasting for thirty days, after which he was to go to Mount Sinai, where he would be given the law by which he would govern his people.

The ancients said that after Moses fasted thirty days, he hated to speak to his Lord because of the odor of his mouth. He ate a plant of the earth and then his Lord said to him: "Why did you break your fast?" Moses said: "0 my Lord, I disliked to speak to You with my mouth not having a pleasant smell." Allah said: "Do you not know, Moses, the odor of the faster's mouth is more fragrant to Me than the rose. Go back and fast ten days; then come back to Me." Moses did what Allah commanded.

Moses Speaks to Allah - Qur'anic
Almighty Allah declared: And We appointed for Moses thirty nights and added (to the period) ten (more), and he completed the term, appointed by his Lord, of forty nights. And Moses said to his brother Aaron: "Replace me among my people, act in the Right Way (by ordering the people to obey Allah and to worship Him Alone) and follow not the way of the Mufsideen mischi ef makers)."

And when Moses came at the time and place appointed by Us, and his Lord spoke to him, he said: "0 my Lord! Show me (yourself), that I may look upon You."

Allah said: "You cannot see Me, but look upon the mountain if it stands still in its place then you shall see Me." So when his Lord appeared to the mountain, He made it collapse to dust, and Moses fell down unconscious. Then when he recovered his senses he said: "Glory be to You, I turn to You in repentance and I am the first of the believers."

(Allah) said: "0 Moses, I have chosen you above men by My Messages, and by My speaking (to you). So hold that which I have given you and be of the grateful."

And We wrote for him on the Tablets the lesson to be drawn from all things and the explanation of all things (and said): "Hold unto these with firmness, and enjoin your people to take the better therein, I shall show you the home of AlFasiqeen (the rebellious, disobedient to Allah). I shall turn away from My Ayat (verses of the Qur'an) those who behave arrogantly on the earth, in a wrongful manner, and (even) if they see all the Ayat (proofs, evidences, verses, lessons, signs, revelations, etc.), they will not believe in them. And if they see the way of righteousness (monotheism, piety, and good deeds), they will not adopt it as the Way, but if they see the way of error (polytheism, crimes and evil deeds), they will adopt that way, that is because they have rejected Our Ayat (proofs, evidences, verses, lessons, signs, revelations, etc.) and were heedless (to learn a lesson) from them. Those who deny Our Ayat (proofs, evidences, verses, lessons, signs, revelations, etc.) and the Meeting in the Hereafter (Day of Resurrection), vain are their deeds. Do they expcet to be rewarded with anything except what they used to do?" Surah 7: 142-147

The Ten Commandments
Earlier scholars said that The Ten Commandments of the Torah are included in two verses of the Qur'an. Say: "Come, I will recite what your Lord has prohibited you from: Join not anything in worship with Him; be good and dutiful to your parents; kill not your children because of poverty - We provide sustenance for you and for them; come not near to shameful sins (illegal sexual intercourse, etc.) whether committed openly or secretly; and kill not anyone whom Allah has forbidden, except for a just cause (according to Islamic law). This He has commanded you that you may understand. And come not near to the orphan's property, except to improve it, until he (or she) attains the age of full strength; and give full measure and full weight with justice. We burden not any person but that which he can bear. And whenever you give your word (i.e. judge between men or give evidence, etc.), say the truth even if a near relative is concerned, and fulfill the Covenant of Allah. This He commands you, that you may remember." Surah 6: 151-152