This knowledge
is the same personal knowledge already mentioned earlier (2 Peter 1:2) which results in salvation. It is not the fruit of human inquiry but the result of divine initiative. Because they enjoy fellowship with God, they can be sure that God will care for them in this life and help them to serve him.
3 His divine power has granted to us all things that pertain to life and godliness, through the knowledge of him who called us to his own glory and excellence,