John Gill Commentary 1 Kings 11:17

"that Hadad fled, he and certain Edomites of his father`s servants with him, to go into Egypt, Hadad being yet a little child." — 1 Kings 11:17 (ASV)

That Hadad fled
While Joab was burying the slain:

he and certain Edomites of his father's servants with him ;
who either was a king, and these some of his officers and courtiers; or however was of the royal family, and had an equipage, and these some of them:

to go into Egypt ;
that was their view at first setting out, where they might hope for help, at least shelter:

Hadad being yet a little child ;
whom his father's servants hid, while Joab was making the slaughter he did, and took the opportunity of fleeing with him while he was burying the dead.