John Gill Commentary 2 Kings 14:22

"He built Elath, and restored it to Judah, after that the king slept with his fathers." — 2 Kings 14:22 (ASV)

He built Elath
A port which belonged to Edom, (Deuteronomy 2:8) (1 Kings 9:26) which very probably David took from them when he made them tributary, and which they retook when they revolted, and Amaziah got again when he defeated them; and this his son rebuilt and fortified:

and restored it to Judah ;
annexed it to the kingdom of Judah, as in the days of David and Solomon:

after that the king slept with his fathers ;
after the death of his father Amaziah.