10 “He that does sin, is of the devil, because the devil sins from the beginning.” “Is of the devil:” ye know what he means: by imitating the devil. For the devil made no man, begot no man, created no man: but whoso imitates the devil, that person, as if begotten of him, becomes a child of the devil; by imitating him, not literally by being begotten of him. In what sense are you a child of Abraham, not that Abraham begot you? In the same sense as the Jews, the children of Abraham, not imitating the faith of Abraham, have become children of the devil: of the flesh of Abraham they were begotten, and the faith of Abraham they have not imitated. If then those who were thence begotten were put out of the inheritance, because they did not imitate, you, who art not begotten of him, art made a child, and in this way shall be a child of him by imitating him. And if you imitate the devil, in such wise as he became proud and impious against God, you will be a child of the devil: by imitating, not that he created you or begot you.
Source: Homilies on the First Epistle of John (New Advent)