And He [that same Jesus] is the propitiation for our sins [the atoning sacrifice that holds back the wrath of God that would otherwise be directed at us because of our sinful nature—our worldliness, our lifestyle]; and not for ours alone, but also for [the sins of all believers throughout] the whole world.

whoever says he lives in Christ [that is, whoever says he has accepted Him as God and Savior] ought [as a moral obligation] to walk and conduct himself just as He walked and conducted Himself.