I don’t know about scripture, but the general idea is that moustaches are regarded as martial and so peaceful types shave their upper lip. However there is also some biblical idea that men should wear beards ( I vaguely recall something about not using razors or scissors on the face)
Quite how the beheaders in Iraq and Syria manage to keep unshaven upper lips is a bit of a puzzle and may require a Wahhabi or Salafist scholar to answer.
Practical answer from an irreligious, lazy shaver : if you let your beard grow forever, nothing bad happens. Beyond, y’know, sporting a bushy hobo beard.
If you let your moustache grow unchecked however, it starts getting inside your mouth/hanging in front of your mouth, which is annoying as hell.
Isn’t this a IMHO thing ?
religious questions may as well be locked to great debates though, since there will always be someone with a NEW “my preacher said” on the topic…
Seems they are saying that their religion requires them to wear a beard, but the mustache is not mentioned , so can be shaved off. The exclusivity (one is not part of the other) of beard and mustache makes some sense, as they must grow the beard really long, while thats impractical for mustaches…
Or if the question is why bother to shave the mustache if they are going to look like cave men anyway ? Ah, the hairs hang down, and then they poke the lower lip, this leads to irritation even infection.
Also the collection of snot in the mustache is frowned upon,
but there’s no mirrors in rest rooms these days, and its not fashion for men to have makeup compacts… Also the mustache dips into the food/drink , same thing with mirrors…
As for religions defining things a bit different to your common sense ?
One near here was wanting to install an aerial wire around a block of buildings.
There is already is, but as its purpose was to carry electricity, that was therefore ONLY an electricity wire. They wanted a purpose installed the aerial wire, for the purpose of defining the block to be “one” - basically to make it one fenced in area… the local council didn’t agree as it went against principles of “government is for everyone”… public land and infrastructure is for everyone …
I like having a beard, but I can’t have a mustache. If I don’t shave my upper lip every two days, I will get eczema on the third day. Dandruff on the face looks repulsive, so I have to shave the mustache.
But then I look like a Muslim, so I also have to shave the cheeks and soul patch.
But then I have a neck beard, so everything under the jawline has to go, too.
And that’s why I have a chin strap beard.
Surely, there must be other men who shave their mustache for the same reasons, but feel that stopping there is good enough.