Many Christians have thought very little about baptism and its significance in their experience of salvation. If they think of baptism at all, it may be only as a personal decision they made to get baptized or in terms of what they think baptism does not mean or accomplish. The Westminster Confession of Faith says:
Baptism is a sacrament of the new testament, ordained by Jesus Christ, not only for the solemn admission of the party baptized into the visible church; but also, to be unto him a sign and seal of the covenant of grace, of his ingrafting into Christ, of regeneration, of remission of sins, and of his giving up unto God, through Jesus Christ, to walk in newness of life.
WCF 28.1
Baptism makes a person a member of the church (1Cor. 12:13). It is a formal rite, conferring actual membership in the Body of Christ. The person baptized may choose to neglect that membership or abandon it later in life. He may become an unbeliever and apostate, but he can never be a non-Christian.
Baptism is a sign and seal that a person has been united to Christ (Gal. 3:27). It certifies that a person has been grafted into Christ, made part of the covenant of grace, and now partakes of the vine. The baptized person may neglect that union or decide to renounce it later in life. He may be cut off from Christ due to unfruitfulness or fall from grace. But he must be connected to Christ before he can be severed from him. He must be a partaker of grace before he can fall away from it. He is connected to Christ in his baptism.
Baptism is a sign and seal that a person has been regenerated (Tit. 3:5). We know that a person may be outwardly baptized and yet remain inwardly unregenerate. Simon the sorcerer was. But the person who is baptized is part of the regeneration (Matt. 19:28) and shares in the resurrected Israel (Ezek. 37:1-14). He may go on living according to the old man of sin. He may reject the resurrection life which we are offered in Christ. But his baptism will forever testify that the new creation has begun.
Baptism is a sign and seal that one’s sins are forgiven (Acts 2:38). It is a symbolic washing which cleanses our souls and saves us from the judgment to come (1Pet. 3:21-22). The person baptized may choose to walk in unbelief and unrepentance, just as Israel did after they were baptized in the Red Sea, and if he does so, then his sins will not be pardoned. But baptism is a visible sign of God’s promise that our sins are forgiven and that God will remember his promises and not our transgressions on the day of judgment.
Baptism is a sign and seal of a covenant obligation (Rom. 6:3-4). The baptized person no longer belongs to himself. He has died with Christ to sin and been raised with Christ to live in obedience for the glory of God. He may choose to forsake that covenant obligation—he may be unfaithful to it—but he cannot deny that he is so obligated. A person does not choose the nation of his birth, but he is subject to its laws as a citizen nonetheless. So too, the person baptized is forever obligated to life under God’s covenant grace and the law of Christ.
Let us not forget or neglect the significance of our own baptism but be deliberately mindful of what it says to us and about us. Improve your baptism, not by doing it over and over again, but by meditating upon its truth, goodness, and beauty, and endeavoring to live in light of it.
This article says, “The person baptized may choose to neglect that membership or abandon it later in life. He may become an unbeliever and apostate, but he can never be a non-Christian.” Are you saying that he is regenerate, and will go to heaven when he dies?
Certainly not. Anyone who is an unbeliever and apostate will be lost. Being a Christian is a covenantal category of identity, not necessarily as salvific one.