Opening the verse
وَمَا نَتَنَزَّلُ إِلَّا بِأَمْرِ رَبِّكَ ۖ لَهُۥ مَا بَيْنَ أَيْدِينَا وَمَا خَلْفَنَا وَمَا بَيْنَ ذَٰلِكَ ۚ وَمَا كَانَ رَبُّكَ نَسِيًّا
[Gabriel said], "And we [angels] descend not except by the order of your Lord. To Him belongs that before us and that behind us and what is in between. And never is your Lord forgetful -
Narrated Ibn `Abbas:The Prophet (ﷺ) said, "O Gabriel, what prevents you. from visiting us more often than you do?" Then this Verse was revealed:--'And we angels descend not but by Command of your Lord. To Him belongs what is before us and what is behind us..' (19.64) So this was the answer to Muhammad