Read Surah Al-Qadr

ذلك التنزل وعظيم طاعة الملائكة بقوله: {بإذن ربهم} أي بعلم ال...

This is the descent, and the great obedience of the angels, by His statement: {بإذن ربهم}, meaning, by the permission of the Lord who is good to them, nurtures them, and enables them. And their descent to the earth, or the lower heaven, or their drawing near to the believers, begins with their descent {من كل أمر}, meaning, the general matters which they distinguish, by the permission of Allah, into the details of the matters that He wills in that year, at their appointed times, from that night until the same night the following year. Or, it is due to the decree of every thing that will occur in that year. And He referred to the thing as 'amr' (affair) to inform that they do not do anything except by His command. And when Allah mentioned these virtues, the result was that it is characterized by complete safety, just like Paradise - which is its cause - is characterized by it. So, that was a clear indication of its greatness, so He said: {سلام}, meaning, it is very great, {هي}, meaning, it is nothing but safety and goodness, with no evil in it. And this safety and blessing will continue in it {حتى}, meaning, until {مطلع الفجر}, meaning, its rise, the time of its rise, and the place of its rise. There will be no evil in it, just like there is evil in other nights. The sun will not rise in its morning between the horns of Satan, if Allah wills. And this is the secret of Al-Kisa'i's recitation with a kasrah. And Allah knows best. The expression 'حتى' was chosen instead of 'إلى' to convey that what comes after it has the same ruling as what comes before it, so the time of the rise of the dawn is under the same ruling as the night. And Ibn Abbas, may Allah be pleased with him, reported that Jibril, peace be upon him, descends on the night of Qadr with a group of angels, and with him is a green banner that he plants.