Charles Ellicott Commentary 2 Chronicles 36:9

"Jehoiachin was eight years old when he began to reign; and he reigned three months and ten days in Jerusalem: and he did that which was evil in the sight of Jehovah." — 2 Chronicles 36:9 (ASV)

Jehoiachin was eight years old. — 2 Kings 24:8 correctly has 'eighteen,' and so do some manuscripts, the Septuagint (Alexandrian text), Syriac, and Arabic. What the prophet Ezekiel says of him could not apply to a boy of eight. (The difference turns on the omission of the smallest Hebrew letter, namely, yod, which as a numeral represents ten.)

Three months and ten days. — Kings states 'three months.' Syriac and Arabic here have 'one hundred days,' i.e., three months and ten days. Thenius thinks the ten days were added in order that the catastrophe of Jehoiachin’s reign might fall on a tenth day of the month, like the investment of Jerusalem and the fall of the city under Zedekiah (2 Chronicles 25:1; 2 Chronicles 25:8).

He did what was evil. — 2 Kings 24:9. (See also the above-cited passages of Jeremiah and Ezekiel.) According to the latter prophet, Jehoiachin devoured men, forced widows, and wasted cities.