Baptism as it is mentioned in the bible refers firstly to the remission of sins by John the baptist.
The sprinkling is said to be derived from sprinkling with blood of bulls of infants for the purpose of sacrifice to Baal whether that is figurative or literal, I don't know.
There is not enough scripts to suggest that even adult baptism was by immersion or by a jug of water but evangelicals believe that it is by immersion and then they argue if it be one or three dunks. I have seen the ritual performed by jug, single dunk and three dunks in different churches to dunking in the sea.
It is supposed to symbolise a public declaration of conversion these days and there is no magic in baptism, merely a ritual of the various cults that weigh it with the value they seem fit.
It is likely that infant baptism pre dates christianity to dedicate infants to pagan gods. Since infant mortality was high in the old days, the hell doctrines et al, baptising infants was a protection that they would ascend to heaven should they die as babies; the RCC merely incorporated this in their doctrines as they were inventing the religion.
Often debates argue the thief on the cross, "today you shall be with me in paradise" when he converted w/o baptism verses the need to evangelise and baptise converts. Then you really are not saved until you are baptised in the holy spirit and babble in tongues and so on.
Supposedly, baptism is supposed to represent death in christ and resurrection as a new person. This never happens as they all merely emerge as wet sinners. The "old man" is supposed to stay buried and what emerges is supposed to be a new creature in christ. Going by what we observe in RL, these folk really do not change that much and then it becomes the devil's fault that the old man is still around.
I was personally done with the jug and a ceremony with immersion so by all accounts, this atheist is twice saved
Taking the aspects of confessionals whether to someone else or by self proclamation, the need to do penance in whatever form of delcaring oneself a worm, unworthy etc. it really makes the whole idea of jesus dying for our sins pretty moot.
Like they say, there is no such thing as a
free lunch. You are never going to be able to declare you are sinless unless you do some good works whatever that is supposed to mean.
The church of christ folk are really very into this and will do anything to get you dunked asap before the koolaide wears off. My buddy converted at a friday night youth meeting and then they immediately went to the church to baptise him before he could change his mind.
Just like conversion, there is coercion and stories used to guilt folk into taking the "final step"
Pretty silly idea when you really examine the practices.