Water baptism is an outward sign of an inward reality,
not a means to have our sins forgiven.
Too often the religious ppl simply trade one set of works or religious practices/rituals, for another, and make the Old and New Covenants seem like two sides of the same coin, the Jewish side and the 'Christian' side.
That is, like the ppl of the Old had to do THIS to keep covenant with God, and now 'christians' have to do THIS to keep covenant with God.
Almost as if it's the same covenant with different things to do.
Water-baptism doesn't bring anyone into the New Covenant, infant or adult.
Hebrews7:22 That is good to know.
The New Covenant is in Christ Jesus, not our religious rituals.
22By so much was Jesus made a surety of a better testament. 23 And they truly were many priests, because they were not suffered to continue by reason of death: 24 But this man, because he continueth ever, hath an unchangeable priesthood. 25 Wherefore he is able also to save them to the uttermost that come unto God by him, seeing he ever liveth to make intercession for them.
26 For such an high priest became us, who is holy, harmless, undefiled, separate from sinners, and made higher than the heavens; 27 Who needeth not daily, as those high priests, to offer up sacrifice, first for his own sins, and othen for the people’s: for this he did once, when he offered up himself. 28 For the law maketh men high priests which have infirmity; but the word of the oath, which was since the law, maketh the Son, who is consecrated for evermore.
8 Now of the things which we have spoken this is the sum: We have such an high priest, who is set on the right hand of the throne of the Majesty in the heavens; 2 A minister of ethe sanctuary, and of the true tabernacle, which the Lord pitched, and not man. 3 For every high priest is ordained to offer gifts and sacrifices: wherefore it is of necessity that this man have somewhat also to offer. 4 For if he were on earth, he should not be a priest, seeing that there are priests that offer gifts according to the law: 5 Who serve unto the example and shadow of heavenly things, as Moses was admonished of God when he was about to make the tabernacle: for, See, saith he, that thou make all things according to the pattern shewed to thee in the mount. 6 But now hath he obtained a more excellent ministry, by how much also he is the mediator of a better covenant, which was established upon better promises.
7 For if that first covenant had been faultless, then should no place have been sought for the second. 8 For finding fault with them, he saith, Behold, the days come, saith the Lord, when I will make a new covenant with the house of Israel and with the house of Judah: 9 Not according to the covenant that I made with their fathers in the day when I took them by the hand to lead them out of the land of Egypt; because they continued not in my covenant, and I regarded them not, saith the Lord. 10 For this is the covenant that I will make with the house of Israel after those days, saith the Lord; I will put my laws into their mind, and write them in their hearts: and I will be to them a God, and they shall be to me a people: 11 And they shall not teach every man his neighbour, and every man his brother, saying, Know the Lord: for all shall know me, from the least to the greatest. 12 For I will be merciful to their unrighteousness, and their sins and their iniquities will I remember no more. 13 In that he saith, A new covenant, he hath made the first old. Now that which decayeth and waxeth old is ready to vanish away.
Hebrews7:22-8:13
If ppl want to water-baptise themselves or their babies as a sign of what Jesus did for them, or even if they believe it's an act of obedience that THEY MUST keep, then fine, let them, as long as they're not insisting on it for others, or claiming it's a thing we must do to 'enter into the New Covenant', or tell others they're not if they don't do it. That misses what Jesus did on the cross, and the Covenant HE established for us.