Does σπέρματος (descendants/seed) refer to Abraham's direct descendants or the nations in Hebrews 2:16?
It refers to the spiritual descendants of Abraham,Jesus became the primary seed of the Abrahamic covenant, God also desired to select other humans to become a secondary seed,this is indicated by the words of Jesus to the Jews who opposed him:
John 8:39 (NRSV)
Jesus and Abraham
39 They answered him, “Abraham is our father.” Jesus said to them, “If
you were Abraham’s children, you would be doing what Abraham did."
From this we discern that not those descending through the flesh, but those having the faith of Abraham are considered by God as Abraham's seed. The apostle Paul makes it clear when he wrote;
Galatians 3: 29 (AMP)
29 "And if you belong to Christ [if you are in Him], then you are
Abraham’s descendants, and [spiritual] heirs according to [God’s]
The secondary seed," the spiritual heirs according to God's promise", is clarified by Apostle Peter when he wrote that God's promise - "it is an inheritance that is imperishable , undefiled, and unfading, kept in heaven for you."
1 Peter 1:3-4 (NRSV)
A Living Hope in heaven.
3 "Blessed be the God and Father of our Lord Jesus Christ! By his
great mercy he has given us a new birth into a living hope through the
resurrection of Jesus Christ from the dead, 4 and into an inheritance
that is imperishable, undefiled, and unfading, kept in heaven for
Paul also wrote:
Ephesians 1:13-14 (NRSV)
13 "In him you also, when you had heard the word of truth, the gospel
of your salvation, and had believed in him, were marked with the seal
of the promised Holy Spirit; 14 this[a] is the pledge of our
inheritance toward redemption as God’s own people, to the praise of
In his book of Revelation, John further clarified that those "marked with the seal of the heavenly inheritance" numbers 144.000 persons from all nations.
Revelation 14:1-7 (NRSV)
The Lamb and the 144,000
14 "Then I looked, and there was the Lamb, standing on Mount Zion! And
with him were one hundred forty-four thousand who had his name and his
Father’s name written on their foreheads. 2 And I heard a voice from
heaven like the sound of many waters and like the sound of loud
thunder; the voice I heard was like the sound of harpists playing on
3 "And they sing a new song before the throne and before the four
living creatures and before the elders. No one could learn that song
except the one hundred forty-four thousand who have been redeemed from
the earth. 4 It is these who have not defiled themselves with women,
for they are virgins; these follow the Lamb wherever he goes. They
have been redeemed from humankind as first fruits for God and the
Lamb, 5 and in their mouth no lie was found; they are blameless."