The apostle Paul tells us to "be kind to one another." Peter says to "add brotherly kindness" to the other godly virtues God is developing in us. Living according to God's instruction, following the example of Christ and aided by the Holy Spirit, we produce the wonderful, spiritual fruit of kindness.
Martin G. Collins
This passage builds on the implication of grace, that is, the gifts of God alluded to in the previous verses. Grace both enables or empowers us and makes demands on us by putting us under obligation. Titus 2:11-12 tells us that the grace of God teaches us that "denying ungodliness and worldly lusts, we should live soberly, righteously and godly." Receiving the grace of God puts us under obligation to respond.
Peter is teaching that the grace of God demands diligence or effort. Verse 5 reads, "giving all diligence [effort]." In addition, it is helpful to understand that Peter is saying in the word translated as "add" that we are to bring this diligence, this effort, alongside or in cooperation with what God has already given. God freely extends His grace, but it obligates us to respond. We are then to do our part in cooperating with what He has given to us—and He inspired Peter to tell us to do it diligently and with a great deal of effort.
We ministers almost constantly speak of growth. Yet, notice where Peter begins his list of traits we are to become fruitful in: He writes, "Add to your faith." "Add" is woefully mistranslated into the English. Yes, it can mean "add," but it is actually much more expansive than that. "Generously supplement" is a more literally correct rendering, which brings it into harmony with "diligence." In other words, make great effort to supplement your faith generously.
Peter sees faith as the starting point for all the other qualities or attributes. He does not mean to imply in any way that faith is elementary, but rather that it is fundamental or foundational—that the other things will not exist as aspects of godliness without faith undergirding them. In the Greek, it is written as though each one of these qualities flows from the previous ones. We could also say that faith is like the central or dominant theme in a symphony, and the other qualities amplify or embellish it.
How much and what we accomplish depend on where we begin. Peter is showing us that there is a divine order for growth, and it begins with faith.
John W. Ritenbaugh
Faith (Part 5)