Albert Barnes 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)

The text should be read as: when David came to the top of the mount where people worship God. The word “top” here, and in 2 Samuel 16:1, is used almost as a proper name. No doubt there was a high-place on the top of the Mount of Olives.