Therein descend the Angels and the Roh by their Lord's
permission with every matter
It means that the Angels descend in abundance during the night of Al-Qadr due to its abundance blessings. The Angels descend with the descending of blessing and mercy. Just as they descend when the Quran is recite, they surround the circle of Zikir (remeberence of Allah) and they lower their wings with true respect for the student of knowledge
Coming up in the next post: 5th verse of surah Al-Qadr ( the last verse)