Charles Spurgeon Commentary 2 Chronicles 33:1

"Manasseh was twelve years old when he began to reign; and he reigned fifty and five years in Jerusalem." — 2 Chronicles 33:1 (ASV)

Manasseh was twelve years old when he began to reign,

He was, therefore, born after the time when Hezekiah was raised up from the bed of sickness. That prolongation of life was not all mercy: I am not sure that we should be so eager for such an extension of earthly existence either for ourselves or for others. Had Hezekiah been able to foresee what the abominations of the first part of Manasseh's reign would be, were he to come to the throne of Judah, I think that the godly king might have been content to die at once rather than live any longer to become the father of such a sinner, and one who would prove to be such an enemy of the true faith. Manasseh was twelve years old when he began to reign. It was too early for a youth to reign over any nation.

It is a great temptation, and a serious peril, when an individual has too much power before he reaches his manhood. It would have been far better for Manasseh if his accession to the throne had been postponed for a good while. You who are very young, and are entrusted with wealth and position, may God keep you from going wrong! It will need great grace to preserve you in the right path.

And he reigned fifty and five years, in Jerusalem:

Manasseh's was a long reign, a varied reign, and at first a wicked reign of the very worst kind. Sometimes men are spared despite their sin. Manasseh's was one of the longest reigns on record: He reigned fifty and five years in Jerusalem.