By the kingdom of God, He means the mysteries of the kingdom of God, that is, the divine Scriptures, which the Lord committed, first to that former people who had the oracles of God, but secondly to the Gentiles who brought forth fruit. For the word of God is given to none but to him who brings fruit thereof, and the kingdom of God is given to none in whom sin reigns.
Whence came it then that it was given to them from whom it was afterwards taken away? Remember that whatever is given is given of free gift. To whom then He let out the vineyard, He let it out not as to elect already and believing; but to whom He gave it, He gave it with a sentence of election.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).