7:142Al-A'raaf

And We appointed read wa-wā‘adnā or wa-wa‘adnā for Moses thirty nights at the end of which We would speak to him after he has fasted during that period; that was the month of Dhū’l-Qa‘da. He completed the fast. But when it came to an end he disliked the bad odour of his mouth and so cleaned his teeth. God then commanded him to fast for another ten nights so that He may speak to him despite the odour in his mouth as God says and completed them with ten nights of Dhū’l-Hijja. Thus was the time appointed by his Lord concluded the time at which God had promised him to speak to him as forty arba‘īna is a circumstantial qualifier nights laylatan is for specification; and Moses said to his brother Aaron when he was departing to the Mount for the communion with his Lord ‘Succeed me be my deputy over my people and be righteous among them with regard to their affair and do not follow the way of the agents of corruption’ by consenting with them to acts of disobedience.