For if you possess these qualities and continue to grow in them, they will keep you from being ineffective and unproductive in your knowledge of our Lord Jesus Christ.
8. For if these things be in you. Then, he says, you will at length prove that Christ is really known by you, if ye be endued with virtue, temperance, and the other endowments. For the knowledge of Christ is an efficacious thing and a living root, which brings forth fruit.
In these words the apostle comes to the chief thing intended in this epistle - to excite and engage them to advance in grace and holiness, they having already obtained precious faith, and been made partakers of the divine nature. This is a very good beginning, but it is not to be rested in, as if we were already perfect.
Commenting on 2 Peter 1:5-11
For if these things be in you,.... Are wrought in you by the Spirit of God, and exercised and performed by his assistance, who works in his people both to will and do: and abound; increase in their acts and exercises by the frequent performance of them: they make you; both by way of influence and evidence, that ye shall neither be barren nor unfruitful...