The immortal God had to become a mortal man to taste death for mankind and free us from the bondage of sin and death.
In verse 11, Paul continues with the word "for", linking this it to his previous statement in verse 10, "the Leader of our salvation, to make complete the leading of the sons to glory through sufferings." Jesus has completed the Way to salvation on the cross. He has paid the debt of sin, redeemed mankind from the bondage of death, and has ascended on high, seated on the right hand of the Father.
Now he continues, "For He who sanctifies, and those who are being sanctified are out of one."
Let's take a deeper look at the text.
We know that "He who sanctifies" is Jesus. Our Savior, the Captain of our Salvation, is the only one who can make us Holy and set us apart from sin.
"and those who are being sanctified", this is us; all those who believe that Jesus is the Son of God and our Savior. We have been led out of the grasp and bondage of death, He has made us holy, set us apart and made us acceptable to be partakers in the inheritance of the saints in Light, Col 1:12.
Now this is the key statement Paul is building toward in verse 11. "For both", Jesus and us who believe in Him, "are all of one."
Of one what? you might ask. Well I am glad you did.
It is true we are One with Him in Christ as believers, and this is a natural thought one might have concerning this verse, but that is not exactly what Paul is saying here. For the saying in Ephesians that "we are One with Him in Christ", Eph 1:10, is absolutely true, but it is not in the same line of thinking that is in this verse. For in order for us to be exalted on high and seated with Him in heavenly places, Eph 2:6, He first had to be made low, Eph 4:9, John 1:14, in fact as Paul says in verse 9, "But we see Jesus, who was made a little lower than the angels, for the suffering of death crowned with glory and honor, that He, by the grace of God, might taste death for everyone."
Jesus had to, for a short time, be made lower than the angels and become a man, that He might taste death for everyone. The immortal God had to become a mortal man to taste death for mankind.
This is the "one" that is being spoken of in verse 11. That Jesus, the Creator of the universe, had to become a man taking on Him flesh and blood. This word "one" in verse 11 is speaking of "one type", namely mankind. For Jesus first had to become a man and suffer the penalty of sin and death on the cross before He could lead us to glory, exalting us as One with Him in heavenly places.
Paul then continues again with a connecting statement, διʼ ἣν αἰτίαν, for which reason, He is not ashamed or embarrassed to call us His brethren.
What an amazing statement! That Jesus would come down from His place of authority in heaven, Phil 2:7-8, be made like one of us, for the purpose that He could then taste death for us and redeem us from our sin and rescue us from the bondage of eternal death, exalting us and seating us on high with Him in heavenly places as children of God! And in this, Jesus was not ashamed to call us His brethren. He was not embarrassed to be made one of us. How unusual is that? Have you ever seen an earthly king or someone in authority give up their right to power and authority to be one of the common folk? And what's more, to be happy and joyful in the process, for it says in a certain place, that "for the joy He endured the cross", Heb 12:2. Jesus was joyful to fulfill the will of the Father, to taste death for every man, to lead the sons unto glory, and unite us as a family with our Father in heaven.
The Grace of our Lord Jesus Christ be with you all, Amen
Ἡ χάρις τοῦ Κυρίου ἡμῶν Ἰησοῦ Χριστοῦ μετὰ πάντων υμῶν. ἀμην.