We all have a purpose for why we are existing. Fulfilling the purpose for which we are on earth is the greatest fulfillment we can ever attain. We are on this earth basically to do good. If our lives is not in anyway of good or help to anyone then we are not fulfilling purpose. God didn't just create us for creating sake. It should be the concern of everyone to walk in the purpose for which God created them.
Galatians 6:10 - As we have therefore opportunity, let us do good unto all men, especially unto them who are of the household of faith.
Apostle Paul is trying to tell us in this passage how important it is for us to do good to people. We should not neglect the brethren in our midst. One of the reasons why we converge together and not stay in our separate locations or houses is so as to be our support to each other either emotionally, materially, or spiritually.
This doesn't limit it to only our brethren in Christ. We should go as far as extending it to everyone irrespective of the race, tribe or whatever. The parable of the good Samaritan is a perfect example for this. It tells us the story of how someone was lying on the ground helplessly which people passed him by without helping him out. Even his so called fellow people went their way. But a Samaritan who happened to be someone from a far away place saw the victim and took pity on him and did him good like he was his brother.
That's how we as christians are supposed to treat everyone. Doing good is a good thing in the sight of the Lord.