I John 3:14-24 This is how we know....

1 John 3:14-18 The practical expression of loving the brethren is straightforward, but not often practiced. Hating one's brother is equivalent of murdering him, in the same vein as Matthew 5:21-22. Love is demonstrated by laying down our life for another person, just as Jesus did. (Romans 5:8) But laying down one's life is not always as costly as dying to save another. If we see a brother having a need and we have resources of the world, and if we lock the bowels of compassion against him, i.e. do not help him in a practical sense, we do not love him. We fail the lifestyle test. Imagine the polygraph of heaven, being asked by Jesus if there ever was an occasion in which we saw a brother in financial need and we could have helped him, and turned away. Even if he did not ask for help, but we recognized a need. Jesus would be asking, did we love in truth and in deed.

1 John 3:19-24 Many people struggle with assurance of salvation. John is not saying that if our conscience is clear, that is proof of salvation. He is not saying that if we keep His commandments and do the things that please Him then we are saved. That would be legalism, pure and simple.  The command that we believe in Jesus' name and love one another echoes Matthew 22:36-40. But John wraps this into the package that is summarized that it is the indwelling Christ abiding in us, through the agency of the Holy Spirit, that empowers us to do all these things. And that we do these unnatural things is proof to us that we truly have Jesus abiding in us, and we are saved.