Knowing Jesus is to know God the Father, because the Son is the Father's final, complete, and perfect self-revelation, as taught in John 14:7-10. In the opening chapter of the Letter to the Hebrews, we are told that in former times God spoke through the prophets, but that in these last days He has spoken to us by His Son.
The Son is described as the heir of all things, the King of the kingdom of God, and it is through Him that the universe was made, a description that can apply only to God Himself. The third verse further declares that the Son is the brightness of God's glory, expressing an identity relationship: just as light cannot be separated from its source, only God can manifest God's own glory, which means the Son must also be God.
Hebrews goes on to affirm that Jesus is the express image of God's person, again indicating this profound identity: the Son and the Father are distinct Persons, yet both are truly God. The same verse adds that the Son upholds all things by the word of His power, a work that only God can perform; so, if He is who God is, and does what God does, He must indeed be God.
In God's gracious plan of redemption, the Son has by Himself purged our sins, and then sat down at the right hand of the Majesty on high, a position and achievement beyond the reach of any mere human being or angelic messenger. Only the Lord Himself could accomplish such a work, and occupy such a place; therefore, Jesus is truly God.