There are all sorts of ideas floating about today in various circles concerning sanctification. If you are getting confused by them, consider the following:
But grow in (by) the grace (help) and knowledge of our Lord and Savior Jesus Christ (2 Peter 3:16).
More often than not, in NT (Koine) writing, it seems that the Greek “en” (often translated “in”) ought to be translated by one of its other possibilities–“by, with,” etc. Here, I am sure that it should read “by,” as I noted in the parenthesis in the quotation. The idea of a “spherical dative” is foolish here (as in many of the translations made of this important preposition).
What Peter was trying to get his readers to understand is that in order to grow in their faith it takes grace and knowledge—both, of course, applied to daily living—in order to grow. And growth, as one learns more about Christ and becomes more like Him, is what sanctification is all about. That grace (here, “help,” the second meaning of the word grace, is also a more appropriate translation).
Growth comes about as a believer learns more of the Christian faith and is helped by God to practice it. More and more he progressively comes to walk as he should (not, in this life without failures, of course). But if one is a true believer, he grows. He will change. He can because he is a new creation. Sanctification is not “on the spot,” as one modern preacher recently said. Nor does it come about without effort: studying and prayerfully applying scriptural truth. It is the result of knowing God’s truth about putting off the old sinful ways and replacing them with new biblical ones that please God. Growth is a sign of life—in this case, spiritual life. No growth—no life.
Think about this and refuse to be herded by the crowd that teaches that something other than growth is essential.