Al-A'raf 7:142

<h2>Musa fasts and worships Allah for Forty Days</h2><p>Allah reminds the Children of Israel of the guidance that He sent to them by speaking directly to Musa and revealing the Tawrah to him. In it, was their law and the details of their legislation. Allah stated here that He appointed thirty nights for Musa. The scholars of Tafsir said that Musa fasted this period, and when they ended, Musa cleaned his teeth with a twig. Allah commanded him to complete the term adding ten more days, making the total forty. When the appointed term finished, Musa was about to return to Mount Tur, as Allah said, </p><div class="arabic uthmani">يبَنِى إِسْرَءِيلَ قَدْ أَنجَيْنَـكُمْ مِّنْ عَدُوِّكُمْ وَوَاعَدْنَـكُمْ جَانِبَ الطُّورِ الاٌّيْمَنَ</div><p>(O Children of Israel! We delivered you from your enemy, and We made a covenant with you on the right side of the Mount) 20:80. Musa left his brother Harun with the Children of Israel and commanded him to use wisdom and refrain from mischief. This was only a reminder, for Harun was an honorable and noble Prophet who had grace and exalted standard with Allah, may Allah's peace and blessings be upon him and the rest of the Prophets. </p>

And when We did appoint for Moses thirty nights (of solitude), and added to them ten, and he completed the whole time appointed by his Lord of forty nights; and Moses said unto his brother, Aaron: Take my place among the people. Do right, and follow not the way of mischief-makers.

We appointed for Moses thirty nights, and completed (the period) with ten (more): thus was completed the term (of communion) with his Lord, forty nights. And Moses had charged his brother Aaron (before he went up): "Act for me amongst my people: Do right, and follow not the way of those who do mischief."

And We appointed for Musa (Moses) thirty nights and added (to the period) ten (more), and he completed the term, appointed by his Lord, of forty nights. And Musa (Moses) said to his brother Harun (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 Mufsidun (mischief-makers)."

And We appointed to Moses thirty nights, and completed them with ten; and thus the time appointed by his Lord was forty nights. And Moses said to his brother Aaron: “Take my place among my people, and be upright, and do not follow the way of the mischief-makers.”