Does the Quran establish the prohibition of shaving the beard and the obligation of letting it grow, given that the Book omits nothing, major or minor, without enumerating it, and that the narrations of the Messenger on this topic are merely Sunnah?

The prohibition of shaving the beard is not explicitly mentioned in the Quran. However, the authentic Sunnah commanded that it be grown, and this command implies obligation. The Quran warned against disobeying the Messenger's command, as Allah Almighty says: (And let those who oppose His command beware, lest a trial strike them or there come upon them a painful punishment) [An-Nur:63]. What the Messenger prohibited is like what Allah prohibited.