Albert Barnes Commentary 2 Chronicles 14:1

"So Abijah slept with his fathers, and they buried him in the city of David; and Asa his son reigned in his stead. In his days the land was quiet ten years." — 2 Chronicles 14:1 (ASV)

Asa his son reigned. If Rehoboam was not more than 21 years old at his accession (1 Kings 12:8 note), Asa, when he mounted the throne, must have been a mere boy, not more than 10 or 11 years of age.

The land was quiet ten years. The great blow struck by Abijah (2 Chronicles 13:15–19), his alliance with Syria (1 Kings 15:19), and the rapid succession of sovereigns in Israel during the earlier part of Asa’s reign (1 Kings 15:25–33) would naturally prevent disturbance on the part of the northern kingdom. The tender age of Asa himself would be a bar to warlike enterprises on the part of Judah.