How do we know that not everyone is a child of God?

The concept of universal fatherhood of God is refuted in Scripture. Jesus makes a clear distinction in John 8:44, identifying certain individuals as being children of the devil, indicating that their actions and beliefs set them apart from those who are genuinely of God. The Scriptures support this by showing that those who do not heed Christ's call and believe in His redemptive work are not recognized as God's children. This further emphasizes the necessity of genuine faith and acceptance of divine truth in defining one as a child of God.