# for life and godliness

"for a godly life" 

# through the knowledge of him who called us

You may need to make specific that it is Peter and his readers who know God. Alternate translation: "through our knowledge of God, who called us" or "because we know God, who has called us"

# through his own glory and excellence

"by showing us his own glory and greatness" or "to share his own glory and excellence"