“29And if you are Christ’s, then you are Abraham’s offspring, heirs according to promise.” (next verse)…4:1 ~“1I mean that the heir, as long as he is a child, is no different from a slave, though he is the owner of everything,”
Paul declared that whoever is Christ’s is an heir according to all God’s promises but even an heir is still like a slave as long as they are an immature child. The original Greek distinguishes between huios/sons and tekna/children. Jesus wasn’t called a huios Son until he was baptized and the Spirit descended on him like a dove; then Father said “This is my beloved huios Son…”
Before that we have no record of Jesus ever using the Father’s divine power or authority because “though he was owner of everything, he was no different than a slave.” The next few verses also describe things that applied to Jesus (The Son) and us as sons. ~
“4But when the fullness of the time came, God sent forth His Son, born of a woman, born under the Law, 5so that He might redeem those who were under the Law, that we might receive the adoption as sons.”
Even Jesus was born under the LAW so that future generations could be redeemed from the LAW and receive sonship and the inheritance!
The way Jesus lived (under the LAW) is not the way we live. We are not as he was in this world; we are now in this world as he is now! (1 John 4:7)
We must simply believe and receive the truth that we have been crucified with Christ to the LAW and the world and are huios/sons of God by faith alone! (Gal.2:19-20)
“26For you are all sons of God through faith in Christ Jesus.” Gal.3:26
Romans 8 distinguished between tekna/children and huios/sons this way ~
“14For all who are led by the Spirit of God are sons of God. 15For you did not receive the spirit of slavery to fall back into fear, but you have received the Spirit of adoption as sons, by whom we cry, “Abba! Father!”16The Spirit himself bears witness with our spirit that we are children of God!”
Slavery/fear/childhood is all LAW based works of the flesh. Following the Spirit by faith in our permanent righteousness in Christ is the way of freedom and inheriting all of God’s promises as huios/sons!
Because it’s not about what we do. It’s about what He did! So that it’s about who we believe we are now in Christ!
“6Then He said to me, “It is done. I am the Alpha and the Omega, the beginning and the end. I will give to the one who thirsts from the spring of the water of life without cost.7“He who overcomes will inherit these things, and I will be his God and he will be My son.” ~Rev.21:6,7
Paul prayed to the faithful followers in Ephesus ~ “18I pray that the eyes of your heart may be enlightened, so that you will know what is the hope of His calling, what are the riches of the glory of His inheritance in the saints, 19and what is the surpassing greatness of His power toward us who believe.
The riches of the glory of Christ’s inheritance is IN US and it part of it is His great power towards those who believe! We receive this by the Holy Spirit opening our eyes and revealing it by his wisdom and insight in the knowledge of God (see previous v.17)
Don’t believe it when people quote the Old Covenant prophecy ~ ““What no eye has seen, nor ear heard, nor the heart of man imagined, what God has prepared for those who love him” because Paul quoted that in 1 Cor.2 and continues in the very next verses to declare how Holy Spirit now reveals them to us!
We have already been given every spiritual blessing, the very inheritance of Jesus and all these things are revealed by the Spirit of God; even the very depths of God! They are all spiritually discerned and cannot be understood by human wisdom but God has given us HIS spirit and His spirit reveals to us all that we have already been freely given!
We simply need to ask, seek and knock more and it will be revealed!