Proverbs 27:17 says, “Iron sharpens iron, and one man sharpens another.” When iron blades are rubbed together, each becomes sharper and thus more effective. Likewise, when believers are involved in one another’s lives, mutual edification occurs. Ecclesiastes 4:9-12 is a similar passage: “Two are better than one, because they have a good reward for their toil. For if they fall, one will lift up his fellow. But woe to him who is alone when he falls and has not another to lift him up! Again, if two lie together, they keep warm, but how can one keep warm alone? And though a man might prevail against one who is alone, two will withstand him—a threefold cord is not quickly broken.” Humans were created for fellowship (Genesis 2:18). When we’re living in healthy fellowship, we rely on one another and help one another. It is often thought that the threefold cord of Ecclesiastes 4:12 refers to two people in relationship who are submitted to God. It is true that fellowship is beneficial for humans in general, but all the more so for Christians (Matthew 18:19-20).
The New Testament is replete with instructions concerning how believers should relate with one another. They are to do good to each other (Galatians 6:10), bear each other’s burdens (Galatians 6:2), forgive each other (Colossians 3:13), restore each other (Galatians 6:1; James 5:19-20), submit to one another (Ephesians 5:21), encourage each other (1 Thessalonians 5:11), admonish and exhort each other (Colossians 3:16; Hebrews 3:13), pursue peace and mutual up-building (Romans 14:19), and stir one another on to love and good deeds (Hebrews 10:24-25). The Body of Christ – believers – should be encouraging and edifying one another. When they do, they are like iron sharpening iron. Each believer becomes more effective in his calling. He comes to know God more and to more effectively carry out the good works for which he has been made (Ephesians 2:10).