Surah Al-A'raf 7:142
۞ وَوَٰعَدْنَا مُوسَىٰ ثَلَٰثِينَ لَيْلَةً وَأَتْمَمْنَٰهَا بِعَشْرٍ فَتَمَّ مِيقَٰتُ رَبِّهِۦٓ أَرْبَعِينَ لَيْلَةً ۚ وَقَالَ مُوسَىٰ لِأَخِيهِ هَٰرُونَ ٱخْلُفْنِى فِى قَوْمِى وَأَصْلِحْ وَلَا تَتَّبِعْ سَبِيلَ ٱلْمُفْسِدِينَ ١٤٢
EnglishSahih International
And We made an appointment with Moses for thirty nights and perfected them by [the addition of] ten; so the term of his Lord was completed as forty nights. And Moses said to his brother Aaron, "Take my place among my people, do right [by them], and do not follow the way of the corrupters."