It is upon Him (swt) to clarify, explain and interpret it. As if Allah (swt) is saying to the Prophet (saws), ‘After you recite it as We have taught you, we will explain and clarify its meaning, interpretation, as well as, its lawful and prohibitions’. Allah 9swt) addresses the prophet (saws) in another verse, saying:

 وَأَنزَلْنَا إِلَيْكَ الذِّكْرَ لِتُبَيِّنَ لِلنَّاسِ مَا نُزِّلَ إِلَيْهِمْ

(And We revealed to you the message that you may make clear to the people what was sent down to them) (An-Nahl: 44)

So, Allah (swt) has clarified the Quran to the Prophet (saws) and he is in turn clarified it to the people. Allah (swt) has made clear what is lawful and unlawful and illustrate its rulings in details. The Arabic word (for Us) indicates that Allah (swt) has obliged Himself to collect the Quran in the Prophet’s heart and clarify its rulings, be obligatory acts, norms and its pillars.