Surah Al-A'raf, ayah 142

۞ وَوَٰعَدۡنَا مُوسَىٰ ثَلَٰثِينَ لَيۡلَةٗ وَأَتۡمَمۡنَٰهَا بِعَشۡرٖ فَتَمَّ مِيقَٰتُ رَبِّهِۦٓ أَرۡبَعِينَ لَيۡلَةٗۚ وَقَالَ مُوسَىٰ لِأَخِيهِ هَٰرُونَ ٱخۡلُفۡنِي فِي قَوۡمِي وَأَصۡلِحۡ وَلَا تَتَّبِعۡ سَبِيلَ ٱلۡمُفۡسِدِينَ ١٤٢

Wawā'adnā mūsā thalāthīna laylatan wa atmamnāhā bi'ashrin fatamma mīqātu rabbihī arba'īna laylatan waqāla mūsā li akhīhi hārūnakhlufnī fī qawmī wa aslih walā tattabi' sabīlal-mufsidīn

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],⁴⁰⁰ and do not follow the way of the corrupters."