Please supply scriptures that explicitly reference this belief.
Ok,
John 3:16-19 speaks of belief in Christ and he did not come to condemn the world but to save it.
The great commission Found in Matthew 28:18-20 to make disciples notice that baptism here as Jesus is speaking is in context to Discipleship
18 And Jesus came and spoke to them, saying, “All authority has been given to Me in heaven and on earth. 19 Go therefore and make disciples of all the nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, 20 teaching them to observe all things that I have commanded you; and lo, I am with you always, even to the end of the age.” Amen.
Jesu continued His earthly ministry three years in which he taught them but many if not all did not fully understand why Jesus came to die Until the resurrection all Gospel was written after the resurrection not before.
After Jesus died and rose from the dead we see HE Jesus was with them 40 days before the ascension to Heaven. The First Time He appeared to them we see in John chapter 20: 22 which John's account is very important because HE was an eyewitness unlike Mark and Luke, they received their information from Peter and Paul and other Apostles.
Also, read John chapter one where John the Baptist says Jesus is the one who will baptize with the Holy Spirt. = the baptism of Christ
Also, the word baptism used also means to enclothe with or emerge depending on the context as it is given in the passage or chapter or verse.
Salvation as we see established in John 3:16-19 and Acts 2: 32, 38-38 again in Roman 10:9-11
Those disciples Like Peter were not waiting in Acts to be saved they were waiting for Power to be witness as Jesu told them in Acts 1:8