John Gill Commentary 2 Samuel 15:32

"And it came to pass, that, when David was come to the top [of the ascent], where God was worshipped, behold, Hushai the Archite came to meet him with his coat rent, and earth upon his head." — 2 Samuel 15:32 (ASV)

And it came to pass, that [when] David had come to the top [of
the mount]
Of the mount of Olives:

where he worshipped God ;
by prayer and praise; here very probably he composed and sung the third psalm (Psalms 3:1–8) , which, as the title shows, was made when he fled from Absalom:

behold, Hushai the Archite came to meet him, with his coat rent, and
earth upon his head ;
in token of mourning, and as a bringer of bad tidings, see (2 Samuel 1:2) ; perhaps he was an inhabitant of Archi, at least originally, which lay on the borders of the tribe of Ephraim, (Joshua 16:2) ; from which he had his name.