I am copying these paragraphs from an online source, because I like how they say it:
The phrase “iron sharpens iron” is found in Proverbs 27:17: "As iron sharpens iron, so one man sharpens another.” There is mutual benefit in the rubbing of two iron blades together; the edges become sharper, making the knives more efficient in their task to cut and slice. Likewise, the Word of God is a “double-edged sword” (Hebrews 4:12), and it is with this that we are to sharpen one another—in times of meeting, fellowship, or any other interaction.
The proverb also indicates the need for constant fellowship with one another. Man was not made to be alone, for did not the Lord God say this, even before the Fall (Genesis 2:18)? How much more, then, after the Fall of Man, do we need to come together with our brothers and sisters in Christ for seasons of fellowship and prayer? Clearly, this was recognized by the saints of the early church (Acts 2:42–47), who “devoted themselves” to teaching, fellowship, communion, and prayer, all corporate activities that provided opportunities for sharpening one another.
There are two points to make about the above proverb. First, the meeting of two together in the Lord’s name will always guarantee blessing. It is a means of grace that the Lord Himself promised—where two or more are gathered in His name, there He is among them (Matthew 18:20). Also, we see a similar meaning in Malachi, for those who feared the Lord talked with each other, and the Lord listened and heard (Malachi 3:16). When we sharpen one another in real Christian fellowship, the Lord bends an ear from heaven and is pleased. Not one word about Him which brings Him glory escapes His notice.
The proverb also indicates the need for constant fellowship with one another. Man was not made to be alone, for did not the Lord God say this, even before the Fall (Genesis 2:18)? How much more, then, after the Fall of Man, do we need to come together with our brothers and sisters in Christ for seasons of fellowship and prayer? Clearly, this was recognized by the saints of the early church (Acts 2:42–47), who “devoted themselves” to teaching, fellowship, communion, and prayer, all corporate activities that provided opportunities for sharpening one another.
There are two points to make about the above proverb. First, the meeting of two together in the Lord’s name will always guarantee blessing. It is a means of grace that the Lord Himself promised—where two or more are gathered in His name, there He is among them (Matthew 18:20). Also, we see a similar meaning in Malachi, for those who feared the Lord talked with each other, and the Lord listened and heard (Malachi 3:16). When we sharpen one another in real Christian fellowship, the Lord bends an ear from heaven and is pleased. Not one word about Him which brings Him glory escapes His notice.
Finally, a knife that has been sharpened will also shine more because all the dullness has been rubbed off its surface. Likewise, we will shine better for our Lord if we do the things mentioned above consistently, all of which will unite us in harmony. “How good and pleasant it is when brothers live together in unity” (Psalm 133:1). Therefore, as the author to the Hebrews says, “And let us consider how we may spur one another on towards love and good deeds. Let us not give up meeting together, as some are in the habit of doing, but let us encourage one another—and all the more as you see the Day approaching” (Hebrews 10:24–25).
