At the end of verse 9 the writer says, "By the grace of God [Christ] tasted death for everyone." The question here is whether "everyone" refers to every human without distinction, or whether it refers to everyone within a certain group. As when I say at staff lunch, "Is everyone present?" I don't mean everyone in the world. I mean everyone in the group I have in mind. What is the group that the writer has in mind: all of humanity without any distinction, or some other group?
Let's let him answer as we trace his thought in the next verses. Verse 10 is the support for verse 9: Christ tasted death for everyone "for it was fitting for him, for whom are all things, and through whom are all things, in bringing many sons to glory, to perfect the author of their salvation through sufferings." In other words, immediately after saying that by the grace of God Christ tasted death for everyone, the writer explains that God's design in this suffering of Christ was to "bring many sons to glory." So verses 9 and 10 go together like this: Christ tasted death for everyone, because it seemed fitting to God that the way to lead his children to glory was through the suffering and death of Christ.
This means that the "everyone" of verse 9 probably refers to every one of the sonsbeing led to glory in verse 10. In other words the design of God—the aim and purpose of God—in sending Christ to die was particularly to lead his children from sin and death and hell to glory. He had a special eye to his own elect children. It's exactly what the gospel of John says in 11:52—that Jesus would die to "gather together into one the children of God who are scattered abroad." These "children of God" that Christ died to gather are the "sons" that God is leading to glory through the death of Christ in Hebrews 2:10.
You can see this in the next verses too. Verses 11 and 12:
For both He who sanctifies [i.e., Christ] and those who are sanctified [the sons he is leading to glory] are all from one Father; for which reason He is not ashamed to call them brethren, saying [in Psalm 22:22], "I WILL PROCLAIM THY NAME TO MY BRETHREN, IN THE MIDST OF THE CONGREGATION I WILL SING THY PRAISE."
In other words the sons that God is leading to glory through the death of Christ are now called Christ's brothers. It was for every one of these that Christ tasted death.
Verse 13 goes on now to call them, not only brothers, but in another sense children of Christ:
And again, "I WILL PUT MY TRUST IN HIM" [Christ's own confession of faith in his Father along with his brothers]. And again, "BEHOLD, I AND THE CHILDREN WHOM GOD HAS GIVEN ME."
Notice, the sons that are being led to glory through the death of Christ are now called children that God has given to Christ. They don't just become children by choosing Christ. God sets his favor on them and brings them to Christ—gives them to Christ. And for every one of these he tastes death and leads them to glory. This is exactly the way Jesus spoke of his own disciples in the prayer of John 17:6: "I manifested Thy name to the men whom Thou gavest Me out of the world; Thine they were, and Thou gavest them to Me." So the picture we have is a chosen people that the Father freely and graciously gives to the Son as his children.
Then notice how verses 14–15 connect the aim of Christ's incarnation and death with this chosen group of children:
Since then the children share in flesh and blood [in other words, since those whom the Father gave to the Son have a human nature], He Himself likewise also partook of the same [human nature], that through death He might render powerless him who had the power of death, that is, the devil; and might deliver those who through fear of death were subject to slavery all their lives [namely, every one of those children and brothers that God had given him to lead to glory by his death].
So here the reason given for the incarnation and the death of Jesus (in verse 14) is that the "children" share in flesh and blood. That's the reason Christ took on flesh and blood. And the "children," according to verse 13, are not humans in general, but children God has given to Jesus. And so the whole design and aim of the incarnation and death of Jesus was to lead the sons, the brothers, the children, whom God gave to Jesus, to glory.
--Excerpt from John Piper's sermon, For Whom Did Jesus Taste Death? (May 26, 1996).
