Jeremiah 52:31
And it came to pass in the seven and thirtieth year of the captivity of Jehoiachin king of Judah, in the twelfth month, in the five and twentieth day of the month, that Evil-merodach king of Babylon in the first year of his reign lifted up the head of Jehoiachin king of Judah, and brought him forth out of prison,
Jehoiachin's captivity began in 597 B.C., when Nebuchadnezzar carried him to Babylonia with other captives including Ezekiel. The verse belongs to the record of the destruction of Jerusalem, which came a few years after the warning about the sacredness of the Sabbath. That warning had promised in God's condescension that if the people would bear no burdens on the Sabbath Jerusalem would stand forever, but if they would not listen and obey in keeping the holy day God would destroy it, and the destruction shown in Jeremiah 52 proves that threat was accomplished.
The verse records that in the first year of his reign Evil-merodach lifted Jehoiachin king of Judah out of prison and showed him royal favor, the notable act of his brief reign. It shows Jehoiachin had then been kept in prison in Babylon for thirty-seven years though he had only contemplated rebellion, a prolonged imprisonment that was unusual and unnecessary, beyond what was needed to secure Nebuchadnezzar's interests, and not excused by the general practice of the age. That needless severity proves real cruelty of disposition in Nebuchadnezzar, like that of Sargon and Asshur-banipal, showing he took pleasure in the wanton infliction of suffering on those who had provoked his resentment.