The Church is Israel[Not National Israel], the Spiritual Kingdom of God, and we know this by many promises made to Israel in the OT times find its ultimate fulfillment in the NT Gospel dispensation, for instance, when Paul wrote to a gentile city church assembly, Corinth, designating them Saints 1 Cor 1:2
2 Unto the church of God which is at Corinth, to them that are sanctified in Christ Jesus, called to be saints, with all that in every place call upon the name of Jesus Christ our Lord, both their's and our's:
The word saints here is the greek word hagios:
set apart by (or for) God, holy, sacred.
They were a people set apart from the world, and when writing his second epistle to them, he applied OT promises made to Israel , he applied to them 2 Cor 6:14-18
14 Be ye not unequally yoked together with unbelievers: for what fellowship hath righteousness with unrighteousness? and what communion hath light with darkness?
15 And what concord hath Christ with Belial? or what part hath he that believeth with an infidel?
16 And what agreement hath the temple of God with idols? for ye are the temple of the living God; as God hath said, I will dwell in them, and walk in them; and I will be their God, and they shall be my people.
17 Wherefore come out from among them, and be ye separate, saith the Lord, and touch not the unclean thing; and I will receive you.
18 And will be a Father unto you, and ye shall be my sons and daughters, saith the Lord Almighty. 11
