The seal of the new covenant is not baptism nor the sabbath but the Holy Ghost.
In Ephesians 1:13, Paul tells the believers that they “were sealed with that holy Spirit of promise”. Paul restates in Ephesians 4:30 that believers are sealed with the Holy Ghost saying, “And grieve not the holy Spirit of God, whereby ye are sealed unto the day of redemption.” This seal is not obtained by any works but rather by the simple faith in Jesus Christ. Romans 8:1-14 declares that God has given all believers his holy Spirit:
 There is therefore now no condemnation to them which are in Christ Jesus, who walk not after the flesh, but after the Spirit.
 For the law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death.
 For what the law could not do, in that it was weak through the flesh, God sending his own Son in the likeness of sinful flesh, and for sin, condemned sin in the flesh:
 That the righteousness of the law might be fulfilled in us, who walk not after the flesh, but after the Spirit.
 For they that are after the flesh do mind the things of the flesh; but they that are after the Spirit the things of the Spirit.
 For to be carnally minded is death; but to be spiritually minded is life and peace.
 Because the carnal mind is enmity against God: for it is not subject to the law of God, neither indeed can be.
 So then they that are in the flesh cannot please God.
 But ye are not in the flesh, but in the Spirit, if so be that the Spirit of God dwell in you. Now if any man have not the Spirit of Christ, he is none of his.
 And if Christ be in you, the body is dead because of sin; but the Spirit is life because of righteousness.
 But if the Spirit of him that raised up Jesus from the dead dwell in you, he that raised up Christ from the dead shall also quicken your mortal bodies by his Spirit that dwelleth in you.
 Therefore, brethren, we are debtors, not to the flesh, to live after the flesh.
 For if ye live after the flesh, ye shall die: but if ye through the Spirit do mortify the deeds of the body, ye shall live.
 For as many as are led by the Spirit of God, they are the sons of God.
Furthermore, salvation is not of works but of grace.
 For by grace are ye saved through faith; and that not of yourselves: it is the gift of God:
 Not of works, lest any man should boast.
 For we are his workmanship, created in Christ Jesus unto good works, which God hath before ordained that we should walk in them.