Galatians 4:7 So you are no longer a slave, but a son; and since you are a son, God has made you also an heir.
“no longer a slave, but a son” Paul sums up all his legal metaphors, We are free from the curse of 3:10, we are no longer in the prison of 3:22-23, we are no longer under the “charge” of a pedagogue (3:24-35), that is, the law is not necessary to guide us to Christ anymore. We have found Him! We have arrived! We are no longer slaves as noted in 3:28, or 4:1, and finally, we are no longer subject to the guardians and trustees of 4:2. The “time set” by our Father in Heaven has come! We are truly “sons.”
“also an heir.” Our Father is no common person. He is the Lord of the universe. In the covenant “last will and testament,” referenced in 3:15, there is a tremendous promise of inheritance, through grace, that each of us now receives -- not a "pie in the sky," "someday I'll go to heaven" kind of inheritance, but the inheritance of a new life, of new creation, of being made new in the here and now.