وَوَاعَدْنَا مُوسَىٰ ثَلَاثينَ لَيْلَةً وَأَتْمَمْنَاهَا بِعَشْرٍ…
Source: Source: duas.org · zilhajj-amaal-1st-10-days
wa wa`adna musa thalathina laylatan wa atmamnaha bi`ashrin fatamma miqatu rabbihi arba`ina laylatan wa qala musa li'akhihi haruna ikhlufni fi qawmi wa aslih wa la tattabi` sabila almufsidina
And We appointed with Moses a time of thirty nights and completed them with ten more, so the appointed time of his Lord was complete forty nights, and Moses said to his brother Aaron: Take my place among my people, and act well and do not follow the way of the mischief-makers.
Reference / Source
Source: duas.org · zilhajj-amaal-1st-10-days