Iron in iron is causing to sharpen; and a man causes the faces of his friend to sharpen. Prov 27:17 literal
Iron doesn’t sharpen iron. Google it. Try it. What is it that sharpens iron? A stone…
“Faces” is the literal translation of the word. It is a plural word.
Being a proverb of wisdom this may be more puzzling then we think. The verb sharpen is in the Hiphil causative form and not the normal Qal active. There are no marks of the accusative to indicate what exactly is being sharpened. The Hiphil verb means that the object, iron, causes something else to sharpen. It is not iron itself sharpening. Another thing to learn is that the Hebrew Scriptures lists metals as prophetic symbols—gold, silver, bronze, iron—like four classes.
The verb to come in in the Hiphil form would be properly translated “causes to come in” which is why it is typically condensed to “bring in”. Similarly to remember in the Hiphil would be “to remind”.
Let’s make things more interesting. The verb sharpen (Strong’s #2300) is only found 6 times in the Bible. In every other context it used of judgment. Habakkuk gives us a clear picture of its figurative use:
“their horses also are swifter than the leopards, and are more fierce than the evening wolves” Habakkuk 1:8 KJV
Sharp is figuratively used of a fierce face like that of an evening wolf. What is an evening wolf?
“Benjamin is a ravenous wolf; In the morning he devours the prey, And in the evening he divides the spoil.” Genesis 49:27 NASB
That’s what the Bible calls “sharp”. Taken prophetically, a man causing his friend’s face to gnarl up like a wolf sounds like the face of Scribes and Pharisees at the teaching of Jesus.