Paul proved that Christians are children of God as he taught that with the advent of faith, Christians are no longer under any dispensation of law. We are sons of God through faith in Christ Jesus. Our baptism means putting on Christ. In Christ Jesus, there is no discrimination, no Jew nor Greek. If we are Christ's, then we are Abraham's offspring and heirs according to promise. The heir can be compared to a slave because though he owns the estate, he could not exercise control being under a guardian. So when we were children, we were slaves to the spiritual elements, but at the appointed time, God sent His son who was born of a woman and even under the law to redeem those who were under the law, thus enabling them to receive adoption as sons leading to freedom through Christ. When we become sons of God, we receive the spirit of His son in our hearts and by so doing we are no longer slaves but sons of God and, therefore, heirs.