Albert Barnes Commentary 1 Kings 11:29

"And it came to pass at that time, when Jeroboam went out of Jerusalem, that the prophet Ahijah the Shilonite found him in the way; now [Ahijah] had clad himself with a new garment; and they two were alone in the field." — 1 Kings 11:29 (ASV)

At that time - Probably after Jeroboam’s return from Egypt (see 1 Kings 11:40).

The Shilonite - An inhabitant of Shiloh in Mount Ephraim, the earliest and most sacred of the Hebrew sanctuaries (Joshua 18:10; Judges 18:31; 1 Samuel 4:3, etc.).