This is how we know who the children of God are and who the children of the devil are; Anyone who does not do what is right is not a child of God; nor is anyone who does not love his brother (1 John 3:10).
Someone has said that people may be divided into two classes, the righteous and the unrighteous, and the classifying is always done by the righteous! Certainly it is true that humanity is divided into two classes—not three, as we often fondly imagine. We would like to think there are the children of the devil, the children of God, and then a vast group in between who are morally neutral, neither devilish nor godly. But God says
No, there are not three classes.
Nor is there one class. There are many today who would have us believe that all people everywhere are, by virtue of their natural birth, children of God. But the Bible never sustains that idea for even a moment. These words of John are the echo of the words of the Lord Jesus Himself when He said to certain Pharisees of His day,
You belong to your father, the devil, and you want to carry out your father’s desire (John 8:44). This is what the phrase children of the devil means. It does not mean that the devil created them, but it means that they reflect the nature and characteristics of the devil.