John Gill Commentary Jeremiah 48:37

"For every head is bald, and every beard clipped: upon all the hands are cuttings, and upon the loins sackcloth." — Jeremiah 48:37 (ASV)

For every head [shall be] bald, and every beard clipped

Men, in times of mourning, used to pluck off the hairs of their head till they made them bald, and shaved their beards; which, as Kimchi says, were the glory of their faces; see (Isaiah 15:2).

upon all the hands shall be cuttings

It was usual with the Heathens to make incisions in the several parts of their bodies, particularly in their hands and arms, with their nails, or with knives, in token of mourning; which are forbidden the Israelites, (Deuteronomy 14:1).

and upon the loins sackcloth

This is a well known custom for mourners, to put off their clothes, and put on sackcloth; all these things are mentioned, to show how great was the mourning of Moab for the calamities of it.