The cave in which Moses concealed himself while God passed in review before him with His celestial retinue, was the same in which Elijah lodged when God revealed Himself to him on Horeb. If there had been in it an opening even as tiny as a needle's point, both Moses and Elijah would have been consumed by the passing Divine light,  which was of an intensity so great that Moses, although quite shut off in the cave, nevertheless caught the reflection of it, so that from its radiance his face began to shine.  Not without great danger, however, did Moses earn this distinction; for as soon as the angels heard Moses request God to show him His glory, they were greatly incensed against him, and said to God: "We, who serve Thee night and day, may not see Thy glory, and he, who is born of woman, asks to see it!" In their anger they made ready to kill Moses, who would certainly have perished, had not God's hand protected him from the angels. Then God appeared in the cloud.
It was the seventh time that He appeared on earth,  and taking the guise of a precentor of a congregation, He said to Moses: "Whenever Israel hath sinned, and calleth Me by the following thirteen attributes, I will forgive them their sins. I am the Almighty God who provides for all creatures. I am the Merciful One who restrains evil from human kind. I am the Gracious One who helps in time of need. I am the Long-Suffering to the upright as well as to the wicked. I am Bountiful to those whose own deed do not entitle them to lay claim to rewards. I am Faithful to those who have a right to expect good from Me; and preserve graciousness unto the two-thousandth generation. I forgive misdeeds and even atrocious actions, in forgiving those who repent."  When Moses heard this, and particularly that God is long-suffering with sinners,  he prayed: "O forgive, then, Israel's sin which they committed in worshipping the Golden Calf." Had Moses now prayed, "Forgive the sins of Israel unto the end of all time," God would have granted that too, as it was a time of mercy; but as Moses asked forgiveness for this one sin only, this one only was pardoned, and God said: "I have pardoned according to thy word." 
The day on which God showed Himself merciful to Moses and to His people, was the tenth day of Tishri, the day on which Moses was to receive the tables of the law from God for the second time, and all Israel spent it amid prayer and fasting, that the evil spirit might not again lead them astray. Their ardent tears and exhortations, joined with those of Moses, reached heaven, so that God took pity upon them and said to them: "My children, I swear by my lofty Name that these your tears shall be tears of rejoicing for you; that this day shall be a day of pardon, of forgiveness, and of the canceling of sins for you, for your children, and your children's children to the end of all generations." 
This day was not set for the annual Day of Atonement, without which the world could not exist, and which will continue even in the future world when all other holy days will cease to be. The Day of Atonement, however, is not only a reminiscence of the day on which God was reconciled to Israel and forgave them their sins, but it is also the day on which Israel finally received the Torah.  For after Moses has spent forty days in prayer, until God finally forgave Israel their sins, he began to reproach himself for having broken the tables of the law, saying" "Israel asked me to intercede for them before God, but who will, on account of my sin, intercede before God for my sake?" Then God said to him: "Grieve not for the loss of the first two tables, which contained only the Ten Commandments. The second tables that I am now ready to give thee, shall contain Halakot, Midrash, and Haggadot." 
At the new moon of the month Elul, Moses had the trumpet sounded throughout the camp, announcing to the people that he would once more betake himself to God for forty days to receive the second tables from Him, so that they might be alarmed by his absence; and he stayed in heaven until the tenth day of Tishri, on which day he returned with the Torah and delivered it to Israel.