The one thing that is to define us and is the evidence of those who truly Jesus disciples is love. Love is the sum of the law and the prophets. The kind of radical love that the world so often does not see. The kind of love that God had for us that we show the same kind of love to those around us. It is the plumb line to know who belong to Him. It's the radical agape love that Paul so clearly talks about here
1 Corinthians 13
4 Love is patient, love is kind. It does not envy, it does not boast, it is not proud. 5 It does not dishonor others, it is not self-seeking, it is not easily angered, it keeps no record of wrongs. 6 Love does not delight in evil but rejoices with the truth. 7 It always protects, always trusts, always hopes, always perseveres.
The same kind of love Jesus speaks of here
Matthew 5
43 "You have heard that it was said, 'Love your neighbor and hate your enemy.' 44 But I tell you, love your enemies and pray for those who persecute you, 45 that you may be children of your Father in heaven. He causes his sun to rise on the evil and the good, and sends rain on the righteous and the unrighteous. 46 If you love those who love you, what reward will you get? Are not even the tax collectors doing that? 47 And if you greet only your own people, what are you doing more than others? Do not even pagans do that? 48 Be perfect, therefore, as your heavenly Father is perfect.