Peter's second letter has been full of warnings not to go backwards, reminding the early church to beware of false teachers and stay true to the Holy Scriptures (2 Peter 1:19-21).  But in this last verse before his martyrdom, he reminds them that they are also designed to grow up – into Christ.  Yes, it is most important to identify heresy and to steer well clear: but heresy hunting can become almost a 'professional' Christian activity.  However many errors are denounced, if we do not grow into the likeness of Jesus Christ, we have missed the point.
 
To grow in Christ involves increasing our desire to receive His grace.  That starts when we first submit to His conviction of our sin, in repentance and faith.  It continues as we get to know Him.  But we can only extend our depth of relationship if it is based on a true understanding of who He is and what He has done.  Faith which rests on our feelings or subjective experiences will always be deficient. That is why we must rely on what God says about Himself in the Bible.  We have no other reliable evidence (2 Peter 2:12-21).
 
When we grow up as real believers in the Lord Jesus Christ, God gets the glory.  Our faith cannot bring glory to ourselves - it is simply an admission of our utter dependence on the mercy and grace of God.  Our knowledge cannot glorify us either - it has come from God, and holding it simply makes us more accountable.  No, God gets the glory whenever sinners seek their Saviour, when the poor in spirit receive their inheritance and when the persecuted are sustained to keep going because they hope in Christ.  He is the most wonderful Saviour ever!

Physical growth requires a combination of nutrition and exercise.  Likewise, growing up in Christ demands that we are nourished by the truth of who He is, what He has said and done; and also that we exercise our faith in obeying what we learn and keep safe by refusing to accept or obey false teaching.  May the Lord help us all to love the truth, obey the truth and stay true to Jesus Christ.