“. . . His Son . . . [is] . . . the brightness of His glory and the express image of His person” (Hebrews 1:3).

The Lord Jesus cannot be expressed fully in words.
The same is true for the Father. His glory is so powerful and strong, no man can see Him and live (Exodus 33:20). He told Moses that he, Moses, cannot see His face, for no man can see Him and live.
God set up the perfect plan.
He sent His only Son to the earth to save and redeem mankind. He sent Jesus to offer life to the world.

Then, He sent the Holy Spirit, who is the Spirit of the Father and of Jesus Christ.
What a wonderful, perfect, glorious plan!

Jesus: the Exact Representationof God’s Nature

Again, when we try to “express” or “explain” Jesus Christ, there are no words to express Him fully, neither His Person nor His glory.
Jesus is an eternal revelation, just as the Father is an eternal revelation.
The New Testament letters are an attempt to “summarize” or “explain” Jesus Christ, our most holy faith, and much more.
A great concise summary is found in Hebrews 1:3.
Notice that there are two parts to the short “explanation: or “summary” of Jesus:

Jesus is:
1. The brightness of God’s glory
2. The express image of God’s person

Therefore, there is the glory of Jesus. And there is His Person.
The glory of Jesus Christ is inexpressible.
The Person of Jesus Christ is inexpressible.

Then those who feared the Lord spoke to one another,
And the Lord listened and heard them;
So a book of remembrance was written before Him
For those who fear the Lord
And who meditate on His name (Malachi 3:16).