And hath taken of the king's seed, and made a covenant with him, and hath taken an oath of him: he hath also taken the mighty of the land:
And hath taken of the king's seed - Zedekiah, Jechoniah's uncle.
Taken an oath of him - swearing fealty as a vassal to Nebuchadnezzar (2 Chronicles 36:13).
He hath also taken the mighty of the land - as hostages for the fulfillment of the covenant; whom, therefore, Zedekiah exposed to death by his treason.