What about Acts 8 where Phillip was converting the lost in Samaria. Verse 12 and 13 says that when they BELIEVED Phillip preaching the things about Jesus, they were BAPTIZED...every example of conversion in the NT has sinners being saved this way. Here are some scriptures. Please read and study them.; Acts 2:38 they believed (what shall we do) and we’re baptized. Acts 8- the Samaritans and the Ethiopian eunuch. Phillip preached Jesus to him and although nothing is said in the scriptures about Phillip teaching baptism, yet as soon as the eunuch came to some water, he said “See, here is water. What hinders me from being baptized?”” And he was baptized. You see the implication. Phillip MUST HAVE TAUGHT baptism. How else would the eunuch have known to do it. ? Then we have Acts 9 the conversion of Saul (Paul). Obviously he believed on the road to Damascus when he talked to Jesus, and he asked, “what would you have me do Lord? This was the perfect place for Jesus to say, you don’t have to do anything you are already saved. Or why didn’t Jesus ask him to say @The
sinners prayer” ( not found ANYWHERE in the Bible). Jesus didn’t say there’s nothing you need to do, instead he said “ Go into the city and there it will be told you what you MUST DO”.. later in Acts 22:16 Paul is recounting his conversion to the Jewish mob and he said after 3 days Ananias came to him and told him to “ A rise and be baptized and WASH AWAY YOUR SINS”. This corresponds completely with what Peter said about baptism in Acts 2:38 @baptism for the remission of sins. Quickly, I will just mention Lydia, Acts 16:14,15 ( beloved and was baptized) and the Phillipian jailor. He was told to believe and he would be saved then they taught him the word of the Lord and he was baptized in the wee hours of the morning. They didn’t wait bc baptism was essential to salvation. Everywhere in the NT people obeyed the instructions in Mark 16:16. You will find no contradiction. I left out Acts 10 the conversion of Cornelius ( by mistake) but the apostle Peter COMMANDED them to be baptized inverses 47 and 48. Jesus himself commanded baptism in the great commission in Matthew 28.:18,19. I don’t have a problem believing Mark 16:16 but if you have doubts then I hope you will take the time to study each one of these conversions and see for yourself that belief and baptism equals salvation. God bless.