Excerpt from sermon on 1 Peter 1:2

Under the Law, the people vowed to be obedient to the Book of the Covenant, and Moses sprinkled their bodies with the blood of the covenant sacrifices (Exodus 24:3-8).

Under the Gospel, the Holy Spirit sanctifies us for obedience to the Lord Jesus Christ and sprinkling our hearts with the blood of Christ.

Baptism is a sign and seal of the sprinkled blood of the new covenant of grace (1 Peter 1:2; WCF 23.1, 4), in which we draw near to God boldly and freely, “with our hearts sprinkled clean from an evil conscience and our bodies washed with pure water.” (Hebrews 10:22; WCF 23.3)

Baptism is a sign and seal of our “new birth and giving up unto God, through Jesus Christ, to walk in newness of life.” (1 Peter 1:3; WCF 23.1)

Baptism is a sign and seal of  “our faith and obedience unto God.” (1 Peter 1:2; WCF 23.4). It is through obedience to the truth of God’s word that we purify our souls with the help of the Holy Spirit. (1 Peter 1:15, 18)

Baptism is a sign and seal of our giving up our names unto God and taking God’s triune Name upon ourselves — Father, Son, and Holy Spirit. (1 Peter 1:2; Matthew 28:19; WCF 23.1; WLC Q167)