Philo Judaeus De Sacrificiis Abelis Et Caini 89

[89] Now the commandment is as follows: "And it shall be," say the scriptures, "when God shall bring thee forth into the land of the Canaanites, in the manner which he swore to thy fathers, and shall give it to thee, that thou shalt set apart unto the Lord all that openeth the womb of all thy flocks, and of all the beasts which thou hast, and shalt set apart all the males for the Lord. Every offspring of an ass that openeth the womb shalt thou exchange for a sheep; and if thou dost not exchange it thou shall redeem it with money." ¹ For that which openeth the wound is Abel, that is to say, a gift, the first-born, and you must examine how and when it is to be offered up;