Jamieson, Fausset and Brown on Ezekiel 23:16

16. sent messengers ... into Chaldea--(Eze 16:29). It was she that solicited the Chaldeans, not they her. Probably the occasion was when Judah sought to strengthen herself by a Chaldean alliance against a menaced attack by Egypt (compare 2Ki 23:29-35; 24:1-7). God made the object of their sinful desire the instrument of their punishment. Jehoiakim, probably by a stipulation of tribute, enlisted Nebuchadnezzar against Pharaoh, whose tributary he previously had been; failing to keep his stipulation, he brought on himself Nebuchadnezzar's vengeance.