وَوَٰعَدْنَا مُوسَىٰ ثَلَـٰثِينَ لَيْلَةً وَأَتْمَمْنَـٰهَا بِعَشْرٍ فَتَمَّ مِيقَـٰتُ رَبِّهِۦٓ أَرْبَعِينَ لَيْلَةً ۚ وَقَالَ مُوسَىٰ لِأَخِيهِ هَـٰرُونَ ٱخْلُفْنِى فِى قَوْمِى وَأَصْلِحْ وَلَا تَتَّبِعْ سَبِيلَ ٱلْمُفْسِدِينَ
Asad Quran Translation
AND [then] We appointed for Moses thirty nights [on Mount Sinai]; and We added to them ten, whereby the term of forty nights set by his Sustainer was fulfilled.104
And Moses said unto his brother Aaron: "Take thou my place among my people; and act righteously, and follow not the path of the spreaders of corruption."
According to several of the Prophet's Companions, and particularly Ibn 'Abbas, the first thirty nights were to be spent by Moses in spiritual preparation, including fasting, whereupon the Law would be revealed to him in the remaining ten (Zamakhshari and Razi; see also Manar IX, 119 ff.). In Arabic usage, a period of time designated as "nights" comprises the days as well.
Malik Quran Translation
We summoned Musa to the mount of Tur for thirty nights and added ten more to complete the term of forty nights for communion with his Rabb. (Before leaving) Musa asked his brother Haroon (Aaron): "You will be in my place among my people, set a good example and do not follow the way of mischief-makers."
Yusuf Ali Quran Translation
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." 1100 1101
The forty nights' exclusion of Moses on the Mount may be compared with the forty days fast of Jesus in the wilderness before he took up his ministry (Matt. iv, 2). In each case the Prophets lived alone apart from their people, before they came into the full blaze of the events of their Ministry.
When for any reason the man of God is absent from his people, his duty of leadership (khilafat) should be taken up by his brother,-not necessarily a blood-brother, but one of his society or brotherhood. The deputy should discharge it in all humility, remembering three things: (1) that he is only a deputy, and bound to follow the directions of his Principal, (2) that right and justice are of the essence of power, and (3) that mischief gets its best chance to raise its head in the absence of the Principal, and that the deputy should always guard against the traps laid for him in the Principal's absence.
Mustafa Khattab Quran Translation
We appointed for Moses thirty nights then added another ten—completing his Lord’s term of forty nights. Moses commanded his brother Aaron, “Take my place among my people, do what is right, and do not follow the way of the corruptors.”
Piktal Quran Translation
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: Take my place among the people. Do right, and follow not the way of mischief makers.
WawaAAadna moosa thalatheena laylatan waatmamnaha biAAashrin fatamma meeqatu rabbihi arbaAAeena laylatan waqala moosa liakheehi haroona okhlufnee fee qawmee waaslih wala tattabiAA sabeela almufsideena