1. The reason God sent forth His Son, born of a woman, born under the law (Gal 4:4-5)
    Ex 21:23-25, Phil 2:6-8, Gal 3:13, Rom 8:3, Gen 3:15, Mt 1:25, Jn 20:31,1 Jn 5:1, Gal 3:26, Mt 20:28, 1 Jn 4:9-10

In the Old Testament, the same thing was required as a price for wrongdoing. (Ex 21:23-25)

Ex 21:23 And if any mischief follow, then thou shalt give life for life,
24 Eye for eye, tooth for tooth, hand for hand, foot for foot,
25 Burning for burning, wound for wound, stripe for stripe.

According to the prophecies of Christ in the Old Testament, Jesus was born as a man, descended from a woman. (Gen 3:15, Mt 1:25)

Gen 3:15 And I will put enmity between thee and the woman, and between thy seed and her seed; it shall bruise thy head, and thou shalt bruise his heel.

Mt 1:25 And knew her not till she had brought forth her firstborn son: and he called his name Jesus.

Although Jesus is God, the reason Jesus came to this earth as a man was to become a ransom for man’s sins. We must die for our sins. But Jesus, who came as a man, died in our place. (Rom 8:3, Gal 4:4-5, Phil 2:6-8, Gal 3:13, Mt 20:28, 1 Jn 4:9-10)

Rom 8:3 For what the law could not do, in that it was weak through the flesh, God sending his own Son in the likeness of sinful flesh, and for sin, condemned sin in the flesh:

Gal 4:4 But when the fulness of the time was come, God sent forth his Son, made of a woman, made under the law,
5 To redeem them that were under the law, that we might receive the adoption of sons.

Phil 2:6 Who, being in the form of God, thought it not robbery to be equal with God:
7 But made himself of no reputation, and took upon him the form of a servant, and was made in the likeness of men:
8 And being found in fashion as a man, he humbled himself, and became obedient unto death, even the death of the cross.

Gal 3:13 Christ hath redeemed us from the curse of the law, being made a curse for us: for it is written, Cursed is every one that hangeth on a tree:

Mt 20:28 Even as the Son of man came not to be ministered unto, but to minister, and to give his life a ransom for many.

1 Jn 4:9 In this was manifested the love of God toward us, because that God sent his only begotten Son into the world, that we might live through him.
10 Herein is love, not that we loved God, but that he loved us, and sent his Son to be the propitiation for our sins.

Now, if we believe that Jesus is the Christ, we are saved and become sons of God. (1 Jn 5:1, Jn 20:31, Gal 3:26)

1 Jn 5:1 Whosoever believeth that Jesus is the Christ is born of God: and every one that loveth him that begat loveth him also that is begotten of him.

Jn 20:31 But these are written, that ye might believe that Jesus is the Christ, the Son of God; and that believing ye might have life through his name.

Gal 3:26 For ye are all the children of God by faith in Christ Jesus.