See on 1Jo 3:4, and compare 1Jo 2:29. Note the article τὴν, the righteousness, in its completeness and unity. Not merely doing righteous acts. “In his relation to other men he will do what is just; and in his relation to the gods he will do what is holy; and he who does what is just and holy cannot be other than just and holy” (Plato, “Gorgias,” 507).