“Because you are his sons, God sent the Spirit of his Son into our hearts, the Spirit who calls out, "Abba, Father" (v6). Paul said that before Jesus came, people were saved by faith (ch3), yet they were like immature children or slaves, without the freedom of complete access to God (v1-3). “But when the set time had fully come, God sent His Son …” (v4), and now through Jesus we have full membership as sons and daughters in God’s family.
“Since you are His child, God has made you also an heir” (v7). In Christ, we have a wonderful inheritance. The riches of fellowship with God are for today and for eternity.