Mat: 28:5 And the angel answering, said to the women: Fear not you; for I know that you seek Jesus who was crucified. 28:6 He is not here, for he is risen, as he said. Come, and see the place where the Lord was laid.....
......28:18 And Jesus coming, spoke to them, saying: "All power is given to me in heaven and in earth.
28:19 Going therefore, teach ye all nations; baptizing them in the name of the Father, and of the Son, and of the Holy Ghost.
28:20 Teaching them to observe all things whatsoever I have commanded you: and behold I am with you all days, even to the consummation of the world."
Again, in Mark 16:6 Who saith to them: Be not affrighted; you seek Jesus of Nazareth, who was crucified: he is risen, he is not here, behold the place where they laid him......
......16:15 And he said to them: "Go ye into the whole world, and preach the gospel to every creature.
16:16 He that believeth and is baptized, shall be saved: but he that believeth not shall be condemned.
It is this explicit command of Christ that not only instituted the Sacrament of Baptism, but also declared it as being wholly necessary for our salvation.
Prior to this, His command, the old law, i.e. the law of the OT was still the requirement. Now, if you want to debate what happened to people who, not hearing this command, died shortly after this command was given, I would hazzard to guess that if they were just, they made it at least to Purgatory, but I do not know and seriously doubt any one knows exactly how God judged those particular people.
***As I said, Christ did not make Baptism the requirement till after His ressurection: ***
What was it before hand, an elective?
You didn't address my question...
"If baptism is so critically important in terms of salvation and spiritual new birth, why do we find Paul with such an unconcerned attitude towards it?"
And we know that Paul was writing "post resurrection".
***16:16 He that believeth and is baptized, shall be saved: but he that believeth not shall be condemned.***
Interesting to note here that damnation is a result of failure to believe, not of a failure to be baptized.