How do you receive the Spirit?
3 You foolish Galatians! Who has bewitched you? Before your very eyes Jesus Christ was clearly portrayed as crucified. 2 I would like to learn just one thing from you: Did you receive the Spirit by the works of the law, or by believing what you heard? 3 Are you so foolish? After beginning by means of the Spirit, are you now trying to finish by means of the flesh? 4 Have you experienced so much in vain—if it really was in vain? 5 So again I ask, does God give you his Spirit and work miracles among you by the works of the law, or by your believing what you heard? 6 So also Abraham “believed God, and it was credited to him as righteousness.”
7 Understand, then, that those who have faith are children of Abraham. 8 Scripture foresaw that God would justify the Gentiles by faith, and announced the gospel in advance to Abraham: “All nations will be blessed through you.” 9 So those who rely on faith are blessed along with Abraham, the man of faith.
Compare Paul's account of this story with James' account
21 Was not our father Abraham considered righteous for what he did when he offered his son Isaac on the altar? 22 You see that his faith and his actions were working together, and his faith was made complete by what he did. 23 And the scripture was fulfilled that says, “Abraham believed God, and it was credited to him as righteousness,” and he was called God’s friend. 24 You see that a person is considered righteous by what they do and not by faith alone.
You have to look at this story from two different sides, one from Abraham and one from Isaac. Paul is telling us that we are sons of Abraham and that the way we receive the Spirit is by faith. James is saying that without works Abraham's faith is dead. They are both talking about the same thing, how did the faith that Abraham had in the God of resurrection get transmitted from Abraham to Isaac? If Abraham had not transmitted that faith to Isaac then the faith would have died with Abraham.
Now what Paul is saying is he is focusing on how we began by the Spirit. His focus is not on Abraham who is over 100 years old, his focus is on Isaac beginning his walk by faith.
Think about the story, Isaac asks his father, here is the wood but where is the lamb? Abraham tells Isaac that God would provide the lamb. Actually the Hebrew says "God will appear as the lamb" (that is what I am told). That's it, Abraham doesn't tell him anything more till they get to the top of the mountain and he begins to tie up Isaac. So put yourself in the mindset of this 12 or 13 year old boy.
Wait, I know I forgot to take the garbage out last week, I'm sorry. No avail. OK, OK, I know I got a B on that math test, didn't study enough, I was playing too much games, I'm sorry, I promise not to do it again. No avail. Now he is laid out on the altar, Abraham pulls out the knife and is about to kill him when all of a sudden he prays "God, you promised to appear as the lamb!" Boom, the angel appears, stops Abraham, and Isaac is saved. That is how Isaac began a life of faith, he wasn't justified by the works of the law but by faith in the promise of God.
Now consider this from James point of view. If Abraham cannot transmit the faith to his son then his faith is dead. This is how denominations dry up and die. This is what a cult truly is, they stop transmitting the faith in the Savior to the next generation.
Genesis 22:1 Some time later God tested Abraham. He said to him, “Abraham!”
“Here I am,” he replied.
2 Then God said, “Take your son, your only son, whom you love—Isaac—and go to the region of Moriah. Sacrifice him there as a burnt offering on a mountain I will show you.”
3 Early the next morning Abraham got up and loaded his donkey. He took with him two of his servants and his son Isaac. When he had cut enough wood for the burnt offering, he set out for the place God had told him about. 4 On the third day Abraham looked up and saw the place in the distance. 5 He said to his servants, “Stay here with the donkey while I and the boy go over there. We will worship and then we will come back to you.”
6 Abraham took the wood for the burnt offering and placed it on his son Isaac, and he himself carried the fire and the knife. As the two of them went on together, 7 Isaac spoke up and said to his father Abraham, “Father?”
“Yes, my son?” Abraham replied.
“The fire and wood are here,” Isaac said, “but where is the lamb for the burnt offering?”
8 Abraham answered, “God himself will provide the lamb for the burnt offering, my son.” And the two of them went on together.
9 When they reached the place God had told him about, Abraham built an altar there and arranged the wood on it. He bound his son Isaac and laid him on the altar, on top of the wood. 10 Then he reached out his hand and took the knife to slay his son. 11 But the angel of the Lord called out to him from heaven, “Abraham! Abraham!”
“Here I am,” he replied.
12 “Do not lay a hand on the boy,” he said. “Do not do anything to him. Now I know that you fear God, because you have not withheld from me your son, your only son.”
13 Abraham looked up and there in a thicket he saw a ram[a] caught by its horns. He went over and took the ram and sacrificed it as a burnt offering instead of his son. 14 So Abraham called that place The Lord Will Provide. And to this day it is said, “On the mountain of the Lord it will be provided.”