The Bible Says
"When the people heard this, they were cut to the heart and said to Peter and the other apostles, 'Brothers, what shall we do?
Peter replied, 'Repent and be baptized, every one of you in the name of Jesus Christ for the forgiveness of your sins. And you will receive the gift of the Holy Spirit."
Acts 2:37,38

"He said to them, 'Go into all the world and preach the good news to all creation. Whoever believes and is baptized will be saved, but whoever  does not believe will be condemned."
Mark 16:15,16