Galatians 3:14 That the blessing of Abraham might come on the Gentiles through Jesus Christ; that we might receive the promise of the Spirit through faith.
Notice the KJV deliberately use the singular blessing in Galatians 3.
Abraham was promised many things and blessed with many things in scripture. What is that singular blessing that Abraham that Paul was referring to in Galatians 3?
Of course, and nobody is denying that. But the blessings and curses of the law are more than just receiving the Spirit. That is important, yes, absolutely. But a causal reading of the blessings and curses reveals it is much more than that. And you are correct; the word blessing is in the singular when referring to the Spirit because that is one blessing.
Paul uses the plural in:
2 Corinthians 1:20 KJV
20. For all the promises of God in him are yea, and in him Amen, unto the glory of God by us.
He preached all the promises, not just one.
Deuteronomy 28:2-14 KJV
2. And all these blessings shall come on thee, and overtake thee, if thou shalt hearken unto the voice of the LORD thy God.
3. Blessed shalt thou be in the city, and blessed shalt thou be in the field.
4. Blessed shall be the fruit of thy body, and the fruit of thy ground, and the fruit of thy cattle, the increase of thy kine, and the flocks of thy sheep.
5. Blessed shall be thy basket and thy store.
6. Blessed shalt thou be when thou comest in, and blessed shalt thou be when thou goest out.
7. The LORD shall cause thine enemies that rise up against thee to be smitten before thy face: they shall come out against thee one way, and flee before thee seven ways.
8. The LORD shall command the blessing upon thee in thy storehouses, and in all that thou settest thine hand unto; and he shall bless thee in the land which the LORD thy God giveth thee.
9. The LORD shall establish thee an holy people unto himself, as he hath sworn unto thee, if thou shalt keep the commandments of the LORD thy God, and walk in his ways.
10. And all people of the earth shall see that thou art called by the name of the LORD; and they shall be afraid of thee.
11. And the LORD shall make thee plenteous in goods, in the fruit of thy body, and in the fruit of thy cattle, and in the fruit of thy ground, in the land which the LORD sware unto thy fathers to give thee.
12. The LORD shall open unto thee his good treasure, the heaven to give the rain unto thy land in his season, and to bless all the work of thine hand: and thou shalt lend unto many nations, and thou shalt not borrow.
13. And the LORD shall make thee the head, and not the tail; and thou shalt be above only, and thou shalt not be beneath; if that thou hearken unto the commandments of the LORD thy God, which I command thee this day, to observe and to do them:
14. And thou shalt not go aside from any of the words which I command thee this day, to the right hand, or to the left, to go after other gods to serve them.
It would seem odd that God would bless His servants better than His children. Indeed, deliverance is called the children's bread. A women, a Canaanite (not even Jewish):
Matthew 15:22-28 KJV
22. And, behold, a woman of Canaan came out of the same coasts, and cried unto him, saying, Have mercy on me, O Lord, thou Son of David; my daughter is grievously vexed with a devil.
23. But he answered her not a word. And his disciples came and besought him, saying, Send her away; for she crieth after us.
24. But he answered and said, I am not sent but unto the lost sheep of the house of Israel.
25. Then came she and worshipped him, saying, Lord, help me.
26. But he answered and said, It is not meet to take
the children's bread, and to cast it to dogs.
27. And she said, Truth, Lord: yet the dogs eat of the crumbs which fall from their masters' table.
28. Then Jesus answered and said unto her, O woman,
great is thy faith: be it unto thee even as thou wilt. And her daughter was made whole from that very hour.
It was her looking beyond the limitations that He called faith. And she received the children's bread in reward. So even if one demands that these promises only belong to the Jews, we can see that Jesus made them good, even to a despised and cursed Canaanite who had faith. We should be encouraged so much more!