God used different illustrations to drive home the same point. The Galatian saints needed to understand the basis of salvation and they needed to understand the importance of accepting God’s truth. There is no other truth and they and we need to understand this. No one can defy God and be speaking the truth.
An heir does not have the power to take possession of what he has until he is an adult. A child is like a servant in this regard. He is the future controller of the company or whatever it is that is being willed. However, as a child he cannot legally take control.
In verses 1-2 we see that the child that is the heir is under tutors. He or she cannot make wise decisions and thus is under the authority of the appointed guardians. The father of the child sets the terms of the governorship.
God gave that illustration because we understand these things. In verse 3 Paul drew this home to the spiritual situation. God taught Abraham important truths about Himself and His plan for Abraham and his descendants. Abraham taught his son Isaac the truths that God had given him. Isaac did the same for Jacob. Eventually God gave the nation of Israel the law. We have already seen that God gave them the law because of transgressions (sins). As is typical with us as people, the further we are removed from the source, the more corruption there is in the message. By the time Israel was a nation leaving Egypt, they had witnessed much idolatry and they had adopted some of the paganism of the Egyptians. Most of the Jews that left Egypt did not believe in the true God. They had a version of God that was far removed from the facts.
We know that the Pharaoh that lived after the death of Joseph did not know about Joseph and the significance of his family being in the land of Goshen. Thus he took a much different approach to the Jews. We know that the Jews were not being well taught in the fear of the LORD. Thus there were things that were becoming normative to the Jews that were sin. God put the law in place when Israel left Egypt to remind them of Who He was. He showed them that they were not living holy lives and yet that was what was required of God’s children.
In chapter 4:3 Paul began with the phrase “even so we”. He is again addressing the Jews, his people. In the Old Testament dispensation, even the Old Testament saints were generally not well taught. We know that at the time of Christ, there was much distortion of the truth. Jesus often referred back to things that were spoken of by the prophet Isaiah or Jeremiah or even of Abraham. He took man right back to the time of Creation. The Pharisees had flooded the minds of the people with false teaching. The temple was not being used as God intended it to be. Twice Jesus had to cleanse the temple in His 3 1/2 years of public ministry. Most of the O.T. saints were children. We have noted before that in God’s economy, a true believer in God is a child of God. We have already noted that not all the descendants of Abraham were his spiritual descendants. Those in the Old Testament who believed God, like Abraham were children of God, but they were not yet able to have all the benefits of being heirs of the promise because Jesus Christ had not come to fulfil the demands of the law. God knew that Jesus Christ would come. He stated “in the fulness of time”. It was not if, but when. God knew the “when”, and He did provide the necessary piece of the puzzle to make the O.T. saints complete in Christ.
Children do not have the capacity to understand or to think things through properly. Children are easily drawn into the world’s thinking and system. Sadly, if we are honest, we find that even adults are easily drawn into the world’s thinking and system. Especially unsaved adults. They have been groomed by the devil from birth and they cannot think properly because they are in darkness. Without God’s salvation, man cannot think properly.
There were O.T. saints who were true saints of God. They believed the promises of God, but God had not brought the ‘seed of the woman to bruise the head of the serpent’. God was not being unjust with them. Abraham had confidence in the promise of God. He looked forward to the fulfilment of God’s promise in the seed of the woman.
In verse 4 we are reminded that in the fulness of time — at just the right time, God sent forth his Son. Jesus Christ was made of a woman, under the law. Jesus Christ is eternal. He is from eternity past.

John 1:1 In the beginning was the Word, and the Word was with God, and the Word was God.
2 The same was in the beginning with God.
3 All things were made by him; and without him was not any thing made that was made.

Verse 14 of that chapter makes it clear that the Word is Jesus Christ. Verse 1 tells us He was in the beginning and that He is God. Verse 2 reminds us that He was in the beginning with God. Verse 3 tells us that He created all things. Jesus Christ is the second person of the Godhead.
He was made of a woman in that God chose to use a woman (Mary) to give flesh to the eternal Son of God. God could have done this any way He wanted to, but He chose to use the normal process in which any human being comes into this world, to give flesh to His Son.
Why did Jesus need to become flesh? Verse 5 makes this clear. We needed a Redeemer. The Jews need a Redeemer. No one can be saved unless the curse of sin is paid for. Some religions teach that Jesus Christ needed to redeem us from the devil. That is false teaching. God is the One Who cursed man. God’s holiness and righteousness needed to be satisfied. Jesus Christ — the eternal Son of God became flesh and as the sinless Son of God, He could go to the cross and He could shed His blood to make it possible for lost sinners to be forgiven and saved.
The law says we are lost and cursed. The law says that we are headed for hell.

Romans 6:23 For the wages of sin is death; but the gift of God is eternal life through Jesus Christ our Lord.