The first part of verse 3 describes the relationship of Jesus to God the father, “who being the brightness of His glory and the express image of His person”
Now let’s look at the amplified version “He is the sole expression of the glory of God [the Light-being, the out-raying or radiance of the divine], and He is the perfect imprint and very image of [God's] nature."
Now let’s consider this. Jesus is the perfect imprint of God and displays His very nature. So if you want to know what God is like and what He says, then understand that what Jesus does and says in the Gospels is God himself!
Jesus said this in John 14:9, “He who has seen Me has seen the Father.” When you read about what Jesus does, you are actually reading what God does!