What is meant by "He clothed them in His light" in Al-Hasan Al-Basri's saying about those who pray at night: "Because they communed in solitude with the Most Merciful, so He clothed them in His light"?

This narration is from Al-Hasan Al-Basri's sayings, not a Marfu' Hadith (a Hadith directly attributed to the Prophet). Its wording is: It was said to Al-Hasan: Why do those who pray at night have the most beautiful faces? He said: "Because they communed with the Most Merciful, and He clothed them with light from His light." Its meaning is that Allah made light inseparable from them, as if it were clothing. The Arabs use "clothing" to express inseparability, as in His Almighty’s saying: "But the raiment of righteousness – that is best." And His saying "from His light" means from Allah's light, with which He illuminates the heavens and the earth, and it is from the effects of the light of His Face. So there is no impediment for Him to illuminate the face of His believing servant who stands in prayer for Allah. The light is attributed to Allah, but it is not His essence.