Albert Barnes Commentary 1 Kings 15:23

"Now the rest of all the acts of Asa, and all his might, and all that he did, and the cities which he built, are they not written in the book of the chronicles of the kings of Judah? But in the time of his old age he was diseased in his feet." — 1 Kings 15:23 (ASV)

The rest of all the acts of Asa - A few of these are preserved in 2 Chronicles 15:9–15 and 2 Chronicles 16:7–12. From the whole narrative of Chronicles, we gather that the character of Asa deteriorated as he grew old. While he consistently maintained the worship of Yahweh from first to last, he failed to maintain the personal faith and piety that had been so conspicuous in his early youth.

The cities which he built - During the earlier part of his reign, before any serious attack was made upon him, Asa had the prudence to build fenced cities in Judah, with walls and towers, gates and bars, thus strengthening himself against a possible evil day (2 Chronicles 14:6–7).

In the time of his old age - If it has been rightly supposed that Rehoboam was a young man of 21 or 22 at his accession (1 Kings 12:8), Asa’s age at this time must have been less than 50. It may seem strange to speak of “old age” in such a case; but Solomon was regarded as “old” at about 50 (1 Kings 11:4 note).