Because you are His sons, God sent the Spirit of His Son into our hearts, the Spirit who calls out, “Abba, Father.”
Galatians 4:6, New International Version
What is the Apostle Paul saying to us when he said, "God sent the Spirit of His Son into our hearts"? With the Spirit of Jesus dwelling within us, we enjoy an inseparable unity and relationship with God. Being made heirs and co-heirs with Christ, we are now sharers of Christ's sonship through adoption into the divine family of the Trinity.
The Spirit of Jesus in us signifies true sonship.
The gift of true sonship is an incredible privilege because Jesus frees you from being slave to sin in order for you to live in freedom as a son or daughter of God. We sometimes fall back into sinful habits and self efforts. This is because we somehow have forgotten who we are and what we have in Christ. This forgetfulness or spiritual amnesia robs us from an abundant and fulfilling life. This explains why some believers have a one-dimensional relationship with God. They hardly know God's heart and have little awareness of what the Father is doing and thus, they find it hard to follow His lead as Jesus did. If this describes you, it is wise to return to the gospel truth of your identity and inheritance in Christ.
True sonship is a partnership in God's work. We are not saved and then left to our own devices. We are saved for good works. Jesus went about the Father's business through preaching the good news of His Father's kingdom. Like Jesus, we too should partner with our Father to announce His invitation to all who are weary and burdened to come to Him. We can then join our voices together with these sons and daughters of God who are weary and burdened and intimately cry out, "Abba, Father" and find rest for our souls.
True sonship is participation in the divine life of the Trinity. We are invited to a friendship with God. As our friendship grows, God's heart becomes less unfathomable—and even less of a mystery. We may not understand God fully, but our yearning to learn from God will empower our desires to act as a true son and daughter of our Father—leading to a life that is both fruitful and restful.