The terms "baptism" and "repentance" could be stated as actions. Alternate translation: "and he preached that people should be baptized to show that they were repenting" (See: [[rc://en/ta/man/jit/figs-abstractnouns]])
They would repent so that God would forgive their sins. The term "forgiveness" can be stated as an action. Alternate translation: "so that their sins would be forgiven" or "so that God would forgive their sins" (See: [[rc://en/ta/man/jit/figs-abstractnouns]])