What is the interpretation of the verse: (But if they are arrogant—then those who are with your Lord glorify Him by night and by day, and they do not tire) [Fussilat/38], and what is the wisdom behind mentioning night and day, given that angels do not experience night and day?

Angels glorify Allah day and night without ceasing. This glorification, day and night, expresses the angels' continuous worship, and it does not necessarily mean they have a day and night as we know it. The sun and moon are among Allah's creations in the heavens, and they are the cause of day and night on Earth.