That's actually Nativity Hymn No. 1 you are citing HM, but it contains the same theological/ritual concepts, as you have identified. Nativity Hymn No. 21, confusingly, was numbered as Hymn No. 14 in older compilations of Ephrem's hymns. The only online translation I know of for Hymn 21 is this one, by Budge, which is a 19th century translation but still pretty good:
http://www.ccel.org/ccel/schaff/npnf213.iii.v.xv.htmlHere is my exceedingly long article explaining all of these issues about Surat al-Qadr, and showing the parallels:
https://www.academia.edu/13853915/The_Annunciation_of_S%C5%ABrat_al-Qadr_Celebrating_the_Incarnation_of_the_Deity_Q_97_But as you noted in the section from Hymn No. 1, the key is that in Syriac Christianity this night was when the *infinite Lord* descended and became finite, and by his descent his worshipers commune with the deity. On other nights, worship was akin to Jewish worship, but the miraculous descent of the Lord himself on this night made it *incomparably* superior. Within Islam, this descent of the Lord became transformed into a revelation that the Lord gave an angel who gave it to the Messenger who gave it to the believers .... and this game of telephone, which insulated the Lord from his creation out of anti-polytheistic fervor, made the Laylat al-Qadr incomprehensible. No longer did the believer himself directly commune with the deity and the heavens via the Christmas vigil and its concluding Eucharist -- the Lord himself came down to You. In Islam, only the Prophet and Gabriel were uniquely given those roles in a tag-team combination, so there could be no corresponding night of qadr, the revelation was now akin to Jewish revelation. Instead random blessings came down on the believer for random reasons.
Btw, it's important to understand that the noun form Qadr most literally means a "process of measuring," such that it should literally be translated "the night of the process of measuring." Because that is incomprehensible within Islam (what was measured on this night? why would that matter?), it is usually more loosely translated by using other forms of the same roots -- destiny, power, decree. But this confusion is, in my view, all wrong, the literal meaning of the noun is exactly what was intended.
Topic: Laylatul Qadr The Night of Power