Philo Judaeus Quod Deterius Potiori Insidiari Soleat 166

[166] On this account, also, the oracle which bears testimony against this pretended simplicity of Cain, says, "You do not think as you say." ¹ For you say, indeed, that whosoever finds out the ^{2 3} devices of your act will slay you. But you know that it is not every one who will do so, as there are millions of men enrolled in your alliance; but he only who is a friend to virtue and an irreconcileable enemy to you. And God says, he "who slays Cain shall suffer sevenfold." But I do not know what analogy this real meaning of this expression bears to the literal interpretation of it, "He shall suffer sevenfold. For he has not said what is to be sevenfold, nor has he described the sort of penalty, nor by what means such penalty is excused or paid.