Al-A'raf - 7:142

وَوَاعَدْنَا مُوسَى ثَلاَثِينَ لَيْلَةً وَأَتْمَمْنَاهَا بِعَشْرٍ فَتَمَّ مِيقَاتُ رَبِّهِ أَرْبَعِينَ لَيْلَةً وَقَالَ مُوسَى لأَخِيهِ هَارُونَ اخْلُفْنِي فِي قَوْمِي وَأَصْلِحْ وَلاَ تَتَّبِعْ سَبِيلَ الْمُفْسِدِينَ
[7:142]
And We appointed with Musa a time of thirty nights and completed them with ten (more), so the appointed time of his Lord was complete forty nights, and Musa said to his brother Haroun: Take my place among my people, and act well and do not follow the way of the 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 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.