Quran 7:142 — The Purgatory (Al-A'araf)

We summoned Moses for thirty* nights, and completed them by adding ten.* Thus, the audience with his Lord lasted forty* nights. Moses said to his brother Aaron, "Stay here with my people, maintain righteousness, and do not follow the ways of the corruptors."

[7:141] Recall that we delivered you from Pharaoh's people, who inflicted the worst persecution upon you, killing your sons and sparing your daughters. That was an exacting trial for you from your Lord.

[7:143] When Moses came at our appointed time, and his Lord spoke with him, he said, "My Lord, let me look and see You." He said, "You cannot see Me. Look at that mountain; if it stays in its place, then you can see Me." Then, his Lord manifested Himself to the mountain, and this caused it to crumble. Moses fell unconscious. When he came to, he said, "Be You glorified. I repent to You, and I am the most convinced believer."