WLC Q.35: How is the covenant of grace administered under the New Testament?
Under the New Testament, when Christ the substance was exhibited, the same covenant of grace was and still is to be administered in the preaching of the word, (Mark16:15) and the administration of the sacraments of baptism (Matt. 28:19–20) and the Lord’s supper; (1 Cor. 11:23–25) in which grace and salvation are held forth in more fulness, evidence, and efficacy, to all nations. (2 Cor. 3:6–9, Heb. 8:6,10–11, Matt. 28:19)
WCF 7.6.
Under the gospel, when Christ, the substance, (Col. 2:17) was exhibited, the ordinances in which this covenant is dispensed are the preaching of the Word, and the administration of the sacraments of Baptism and the Lord’s Supper: (Matt. 28:19–20, 1 Cor. 11:23–25) which, though fewer in number, and administered with more simplicity, and less outward glory, yet, in them, it is held forth in more fullness, evidence, and spiritual efficacy, (Heb. 12:22–27, Jer. 31:33–34) to all nations, both Jews and Gentiles; (Matt. 28:19, Eph. 2:15–19) and is called the new Testament. (Luke 22:20) There are not therefore two covenants of grace, differing in substance, but one and the same, under various dispensations. (Gal. 3:14, 16, Acts 15:11, Rom. 3:21–23, 30, Ps. 32:1, Rom. 4:3, 6, 16–17, 23–24, Heb. 13:8)