My son-in-law just asked me this question.
1 Peter 3:8 - 22
ESV - 8 Finally, all of you, have unity of mind, sympathy, brotherly love, a tender heart, and a humble mind. 9 Do not repay evil for evil or reviling for reviling, but on the contrary, bless, for to this you were called, that you may obtain a blessing.
For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.