On the Sacrifice of Abel and Cain (112-114)

Having therefore given an account of the dominant and subject divisions of the soul, and having shown what portion in each is male and female, Moses proceeds after this very consistently to explain the divisions of the body. For being well aware that without labour and care it is not possible to obtain a masculine offspring, he proceeds to say, "Every foal of an ass that openeth the womb, thou shalt exchange for the young of a sheep." [*] Which expression is equivalent to, "Exchange all labour for improvement." For an ass is the symbol of labour, being a much enduring animal, and a sheep is the emblem of improvement, as its very name shows, [*]

being a symbol of the care which is required to be expended in arts and professions, and all other things which are matters of instruction, and that with no negligence or indifference, but it is necessary with all anxiety to have prepared one’s mind to encounter vigorously every amount of labour, and to strive not to be held in bondage by ill-considered toil, but to find advance and improvement by pushing on to the most glorious end; for labour is to be endured for the sake of improvement.

But if you indeed receive fatigue from labour, and still your nature does not advance at all on the road to improvement, but is rather opposed to your becoming better by progress, then abandon the pursuit and be quiet, for it is a difficult task to go against nature. On which account the scripture adds: "And if you do not exchange it, you shall ransom it for money;" which means, but if you are not able to exchange labour for improvement, then give up your labour; for the idea of ransoming carries with it the notion of emancipating the mind from vain and unproductive care.