How do we receive adoption as sons according to Galatians 4?

Galatians 4:5 states, 'to redeem them that were under the law, that we might receive the adoption of sons.' This adoption is a gracious act of God. Before the foundation of the world, He chose a people for Himself, and in the throughout human history, particularly at the fullness of the time, He sent Christ to secure that adoption. Those who believe in Christ are united with Him and, as a result, become children of God. This signifies a deep, familial relationship with God, made possible through the redemptive work of Christ, wherein we are called to cry, 'Abba, Father' (Galatians 4:6).