The author uses a question to emphasize that the people will certainly receive punishment if they refuse God's salvation through Christ. Alternate translation: "then God will certainly punish us if we do not pay attention to his message about how God will save us!" (See: [[rc://en/ta/man/jit/figs-rquestion]])
This can be stated in active form. The abstract noun "salvation" can be translated with a verbal phrase. Alternate translation: "The Lord himself first announced the message about how God will save us and then those who heard the message confirmed it to us" (See: [[rc://en/ta/man/jit/figs-activepassive]] and [[rc://en/ta/man/jit/figs-abstractnouns]])