Assurance for the Christian is knowing this
Whoever believes in the Son has eternal life; …
Fear for the non-Christian is knowing this
…whoever does not obey the Son shall not see life, but the wrath of God remains on him. “
To obey is to believe. Believe what though? To believe in a system of salvation, you do this, God will do that. Not at all, but namely, the Holy Spirit stirring your heart to beg for God. You see your situation as separated from your Maker with new eyes. This being something you simply cannot choose to do on your own. It is both initiated and possible through the Spirit’s work alone. You beg for a solution, you will do anything to make right with Him. Yet nothing you can do is sufficient. That’s where you must stop believing in yourself.
To believe is the recognition of that very wrath aimed at you to be unfairly, and lovingly placed on Jesus for your sake. He doesn’t look in you and see someone worthy, or great. He sees a desperate sinner unable to do it on their own. Notice that in your believing, it still has nothing to do with your good action that advances you toward salvation and away from wrath. It is simply to recognize.
To recognize that you are completely broken and doomed without all He is doing. You are a blind man that can simply not choose to see. You are dead and cannot even imagine a way to make yourself alive again. He is the Way, the One who makes you see and live. Your response, not action, not a good doing, not effort, but a God powered response is to recognize. Recognize you cannot do it and doomed, recognize that He is your All in All. He is the One who gives you, the blind man, the idea of needing to see in the first place. He makes it happen if you will trust that the wrath of God that you totally deserve for hating Him in your heart and actions is taken on Jesus. He is mocked, beaten and bruised because of you. Will you recognize that He personally loves you and took that to the cross? To recognize is to bow and worship.