"We may behold Him as in a mirror" by John Calvin

"Paul calls the Son the 'image of the invisible God', meaning by this, that it is in Him alone that God, who is otherwise invisible, is manifested to us, in accordance with what is said in John 1:18, 'No man hath ever seen God: the only begotten Son, who is in the bosom of the Father, hath Himself manifested Him to us.'

For Christ is called the image of God on this ground-- that He makes God in a manner visible to us. The sum is this-- that God in Himself, that is, in His naked majesty, is invisible, and that not to the eyes of the body merely, but also to the understandings of men, and that He is revealed to us in Christ alone, that we may behold Him as in a mirror.

For in Christ He shows us His righteousness, goodness, wisdom, power, in short, His entire self. We must, therefore, beware of seeking Him elsewhere, for everything that would set itself off as a representation of God, apart from Christ, will be an idol."

--John Calvin, Commentaries on the Epistles of Paul the Apostle to the Galatians, Ephesians, Philippians, and Colossians, trans. T.H.L. Parker (Grand Rapids: Eerdmans, 1965), 308. Calvin is commenting on Colossians 1:15. Ephesians 3: 18-19.