The Inklings were an informal group at Oxford University who gathered to talk, eat, share their work, and critique one another’s output. Several of them, such as Owen Barfield and Charles Williams, produced works of high value.
Among Christians, J. R. R. Tolkien and C. S. Lewis remain the best known. Tolkien credited Lewis with encouraging him to finish The Lord of the Rings; and without the influence of Tolkien, C. S. Lewis would probably never have become a Christian or written the Christian works which brought him such prominence. Iron had certainly sharpened iron.
Those who followed Jesus were also sharpened. Thus we are told in Acts 4:13ff that the Pharisees saw that Peter and John were uneducated men and marveled at their boldness. “And they realized they had been with Jesus.” This is a sharpening any of us can experience if we allow Christ’s Spirit to work in us.