Yes absolute requirement of the new covenantIsn't Christ and the forgiveness of sins received? And can they know and believe in that unless that new message of life is explained to them? This was the 1st century world. Wouldn't it be both shown? As those who didn't believe were not baptized.
What is not negotiable to you in regard to true salvation is water baptism. What is not negotiable to me is faith in and obedience to Christ Jesus.
Faith and baptism