Romans 12:14-21 - Christian Responsibilities To The World

In this section, Paul gives instructions concerning how we are to treat those outside the church body.
 

12:14 Bless [desire happiness for] those who persecute you;
bless and do not curse [call down evil on them].

[So far from wishing or praying that evil overtake our persecutors and enemies, we must sincerely desire and pray for their good. It is not sufficient to avoid returning evil for evil, nor even to banish vindictive feelings; we must be able to sincerely desire their happiness. How hard this is for corrupt human nature, everyone who is acquainted with his own heart well knows. Yet this is the standard of Christian temper and character exhibited in the scriptures (Charles Hodge on Romans, p.398)]
12:15 Rejoice with those who rejoice;
mourn with those who mourn.
12:16 Live in harmony with one another.
Do not be proud [snobbish, high-minded, exclusive],
but be willing to associate with people of low position.
Do not be conceited [having too high of an opinion of yourself].
12:17 Do not repay anyone evil for evil.
Be careful to do what is right in the eyes of everybody.

[Take care to preserve an honorable testimony in the sight of all (F.F. Bruce)]

[Sometimes Christians say that if they have a good conscience, they care not what anyone thinks of them. But this is contrary to this precept [to preserve an honorable testimony in the sight of all]. If we are falsely charged, we may commit ourselves to Him who judges righteously. but, so far as is in our power, we are NOT ONLY to avoid what is improper, but to avoid blame or suspicion of what is improper. (Robert Haldane on Romans, pp.571-572, emphasis mine)]
12:18 If it is possible, as far as it depends on you, live at peace with everyone.
12:19 Do not take revenge, my friends, but leave room for God's wrath, for it is written [in Duet. 32:35] : "It is mine to avenge; I will repay," says the Lord.
12:20 On the contrary [in Prov. 25:21-22 it says]: "If your enemy is hungry, feed him; if he is thirsty, give him something to drink. In doing this, you will heap burning coals on his head."

Moffat translation: … for in this way you will make him feel a burning sense of shame.
 
12:21 Do not be overcome by evil, but overcome evil with good.