2 Peter 1:8

For if these things be in you, and abound; if ye not only have these graces in you, but abound or grow in them, both as to the inward degree and outward exercise of them. They make you; either they make you, or declare you, not to be barren, or both; they will be both the causes and evidences of your not being barren. Barren; or, slothful, idle, unactive. Nor unfruitful; void of good works, which are frequently compared to fruits, Matthew 10:7; Genesis 17:19 Galatians 5:22. In the knowledge of our Lord Jesus Christ; i.e. the faith of Christ. But more is implied here than expressed; q.d. They will make you be active and fruitful in the knowledge of Christ, and declare you to be so, and thereby make it appear that ye have not in vain learned Christ.