Galatians 4:6-7

6 And because you are sons, God has sent forth the Spirit of His Son into your hearts, crying out,  “Abba, Father!”

7 Therefore you are no longer a slave but a son, and if a son, then an heir of God through Christ.

you are sons (v.6) — the Galatians were saved (Romans 8:14).

Spirit of His Son (v.6) — Romans 8:16

Abba (v.6) = father in Aramaic — familiar. Father (pater) = father in Greek — title.  So, “Abba, our Father.”

The Spirit enables believers to call God “Father.” It is the Spirit in us who cries “Abba, Father!”

therefore (v.7) = with the effect that …

no longer (v.7) —  you once were

To know God is to acknowledge Him as Father. To be known by God is to be acknowledged as a son.

Paul is urging the Galatians to remember their positions as heirs and sons by grace and not to return to servanthood to the law.