1 John 3:1-3
In 1 John 3:1-3, the author speaks of that great day when we will see Christ face to face. He admits that it is not entirely clear what this will entail, but he does assert on thing very confidently: “when he appears we shall be like him because we shall see him as he is.” But being transformed into the image of Christ is not something that is only a future hope. In the very next verse John asserts “everyone who thus hopes in him purifies himself as he is pure.” As I read the text, it seems to me that the implication is that in our present condition we are also purified as look upon Christ. In our present condition that looking takes place as we “see” Christ in the proclamation and incarnation of the gospel with the eyes of faith. (Cp. the similar line of through in Paul at 2 Cor 3:18-4:6)
Central, then, to growth in holiness (or as it is sometimes called today “spiritual formation”) is looking at Christ.