Living as Children of Light

Ephesians 4:17-32
So I tell you this, and insist on it in the Lord, that you must no longer live as the Gentiles do, in the futility of their thinking.
That, however, is not the way of life you learned  when you heard about Christ and were taught in him in accordance with the truth that is in Jesus.
You were taught, with regard to your former way of life, to put off your old self, which is being corrupted by its deceitful desires; to be made new in the attitude of your minds. and to put on the new self, created to be like God in true righteousness and holiness.
In your anger do not sin: Do not let the sun go down while you are still angry,  and do not give the devil a foothold.
Do not let any unwholesome talk come out of your mouths, but only what is helpful for building others up according to their needs, that it may benefit those who listen.
Get rid of all bitterness, rage and anger, brawling(爭吵) and slander(誹謗), along with every form of malice.  Be kind and compassionate to one another, forgiving each other, just as in Christ God forgave you.
Salvation is God's free gift, but it carries with it the obligation to live and behave from that point on as God wants. 
This means deliberately discarding the old. selfish way of life, shedding former habits - and letting the new life change our thinking and remold our pattern of behavior. Paul does not stop at generalities: he is quite specific in his 'dos' and 'don'ts'. The new life calls for truth and honesty; no harbored grudges(結怨), no spite and bitterness - instead kindness and a new readiness to forgive.
Why
In Jesus Christ we are free from sins, but put off our old self, and made new in the attitude of our minds and put on the new self, created to be like God in true righteousness and holiness.
We have the image of God so do the right thing and be kind and compassionate to one another. Let the love of Jesus Christ could be known to others.
How?
Say the word benefit to others and don't let any unwholesome talk come out of my mouth.