Not as Cain, [who] was of that wicked one, and slew his brother. And wherefore slew he him? Because his own works were evil, and his brother’s righteous.
Berean Study Bible (BSB) - 1 John 3:12 >Do not be like Cain, who belonged to the evil one and murdered his brother. And why did Cain slay him? Because his own deeds were evil, while those of his brother were righteous.
Textus Receptus (TR) - 1 John 3:12 >οὐ καθὼς Κάϊν ἐκ τοῦ πονηροῦ ἦν, καὶ ἔσφαξε τὸν ἀδελφὸν αὐτοῦ. Καὶ χάριν τίνος ἔσφαξεν αὐτόν; Ὅτι τὰ ἔργα αὐτοῦ πονηρὰ ἦν, τὰ δὲ τοῦ ἀδελφοῦ αὐτοῦ δίκαια.