As is written-  “and, once made perfect, he became the source of eternal salvation for all who obey him and was designated by God to be a high priest in the order of Melchizidek.   We have much to say about this, but it is hard to explain because you are so slow to learn.  In fact, though by this time you ought to be teachers, you need someone to teach you the elementary truths of God’s word all over again.  You need milk, not solid food.  Anyone who lives on milk, being still an infant, is not acquainted with the teaching about righteousness.  But solid food is for the mature, who by constant use have trained themselves to distinguish good from evil.  Therefore let us leave the elementary teachings about Christ and go on to maturity, not laying again the foundation of repentance from acts that lead to death and of faith in God, instruction about baptisms, the laying on of hands, the resurrection of the dead and eternal judgment.” (Heb. 5:9 - 6:2).  These teachings, which include baptism, are considered to be so elementary and foundational that they should already be understood and fully accepted. They should not need to be taught again!