“So in Christ Jesus you are all children of God through faith, for all of you who were baptized into Christ have clothed yourselves with Christ. There is neither Jew nor Gentile, neither slave nor free, nor is there male and female, for you are all one in Christ Jesus. If you belong to Christ, then you are Abraham’s seed, and heirs according to the promise. ” [Galatians 3:26-29]
"In Christ Jesus..."
The key point in this passage is “In Christ”. In Christ you are all children of God through faith. In Christ you are all one. In Christ you are all counted as Abraham’s seed and become heirs to the promise. In Christ you are all chosen. [Eph. 1:3]. In Christ you have the redemption through his blood, the forgiveness of sins.
The pronoun “you” here includes both saved Jews and saved Gentiles. Such people are all sons of God through faith in Christ Jesus.
Union with Christ, which takes place at the time of conversion, is confessed in water baptism. This baptism does not make a person a member of Christ or an inheritor of the kingdom of God. It is a public identification with Christ, which Paul speaks of as a “putting on” of Christ. Just as a soldier proclaims himself a member of the army by “putting on” his uniform, so a believer identifies himself as one who belongs to Christ by being baptized in water. By this act he or she publicly expresses submission to Christ’s leadership and authority. He portrays visibly that he is a son of God.
By baptism the believer signifies also the burial of the flesh and its efforts to obtain righteousness. He signifies the end of the old way of life and the beginning of the new one.
The law made distinctions among these classes. For instance, the distinction between Jew and Gentile is insisted on in Deuteronomy. In Christ Jesus these differences disappear, that is, as far as acceptance with God is concerned. A Jew is not preferred over a Gentile, a free man is not more favored than a slave, nor is a man more privileged than a woman. All are on the same level because they are in Christ Jesus.
This verse must not be pressed into meaning something it does not say. As far as everyday life is concerned, God does recognize the distinction between male and female. The New Testament also speaks separately to slaves and masters, husbands and wives, and parents and children. In our heavenly position all believers are the same before God. In our earthly condition we have to submit to our earthly masters.
"They were all baptized into Moses..."
“For I do not want you to be ignorant of the fact, brothers and sisters, that our ancestors were all under the cloud and that they all passed through the sea. They were all baptized into Moses in the cloud and in the sea. They all ate the same spiritual food and drank the same spiritual drink; for they drank from the spiritual rock that accompanied them, and that rock was Christ.” [1 Corinthians 10:1-4]