06-New-Covenant Assurance

According to the New Testament, everyone who believes God’s
promise in the gospel, and trusts Christ, has the Spirit. 1 He must
have the Spirit (John 14:17; Rom. 8:9; 1 Cor. 12:13). He could
only have believed by the power of the Spirit (John 6:44; Eph.
2:8). Furthermore, the Spirit having enabled the sinner to believe,
then indwells him (John 14:17; Rom. 8:9; 1 Cor. 3:16; 1 John
4:13), taking away his fear, giving him the spirit of sonship,
enabling him to call God his Father, sealing him, anointing him,
and witnessing with his spirit that he is indeed a child of God,
having adopted him into his family. In this way, the believer is
assured, and given inexpressible joy and glory, with an increasing
sense of it (Rom. 8:9-17; 2 Cor. 1:21-22; 2 Cor. 3:18; Gal. 3:26 –
4:7; 5:1,13; Eph. 1:13-14; 4:30; 1 Pet. 1:8; 1 John 2:20-27; 3:24;
4:13; 5:6,9-11, for instance). All this was true of New Testament
believers.