Jehoiachin was eighteen years old when he began to reign. Object. He was then but eight years old, 2 Chronicles 36:9. Answ.
1. Both are true; in his eighth year he began to reign with his father, who made him king with him, as divers other kings of Israel and Judah had done in the like times of trouble; and in his eighteenth year he reigned alone.
2. He is called a son of eight years when he began to reign, 2 Chronicles 36:9, because this was the eighth year, not of his age, but of the Babylonish captivity, or bondage; under which both he and his father had been just so long; for it began in the fourth year of Jehoiakim, as it is affirmed Jeremiah 25:1, and continued all his reign, which lasted eleven years, 2 Kings 23:36; and so the first year of Jehoiachin was precisely the eighth year of that captivity. And this is certain, that the years of kings mentioned in Scripture are not always accounted from the beginning of their age, but from some other remarkable time or thing: thus Saul, when at man's estate, is called the son of one year, 1 Samuel 13:1, of which See Poole on "1 Samuel 13:1" and Ahaziah (whose father lived only forty years, 2 Chronicles 21:20) is called a son of forty and two years when he began to reign, 2 Chronicles 22:2, because that was the forty and second year of the reign of Omri's family, as most think. And therefore it cannot seem strange if the years of this king be computed, not from his birth but from the beginning of so great and famous a change of the Jewish affairs, as this captivity made; this being the usual way of the Romans and Greeks, and other more ancient and eastern nations, to compute the times from the great changes and revolutions happening among them. And that this was the practice of the Jews in the computation of these very times, is evident from the use of it in the Prophecy of Ezekiel, Ezekiel 1:2, which was the fifth year of Jehoiachin's captivity; and Ezekiel 33:21, in the twelfth year of our captivity; and Ezekiel 40:1, in the twenty-fifth year of our captivity.
3. To all this might be added, that some here acknowledge an error of the scribe, and affirm, that in the first and best copies, in 2 Chronicles 36:9, it was not eight, but eighteen; which they gather from hence, because those two ancient and venerable translators, the Syriac and Arabic, read there, as it is here, was eighteen years old; which, they say, they would never have presumed to do, if they had not so read it in those Hebrew copies, out of which they drew their translation, or in some of them. He reigned in Jerusalem three months, and ten days, which are added, 2 Chronicles 36:9. But such small sums are frequently omitted in great numbers. See Poole on "Genesis 15:13"; See Poole on "1 Kings 16:8".