The Certainty of Sonship
In Old Testament times, God’s people, though children, looked no different from slaves as they were under a guardian – the law. We ourselves were once slaves to the elementary principles of this world, trying and failing to justify ourselves by our works. But God has now sent his Son into the world, and through Jesus we have been adopted as God’s children. Because we are God’s children through Christ, God has also sent the Holy Spirit, the Spirit of his own Son, into our hearts to remind us of our status as his children.