Deuteronomy 15:19

What did Moses mean by making this prohibition, except to forbid those who have begun to live aright to engage in human occupations? To plow with the firstborn of a cow is to display the beginnings of one's conversion in carrying out public activities. To shear the firstborn of sheep is to strip the cover of secrecy from our first good works and display them to human eyes. Therefore we are forbidden to work with the firstlings of cattle. When we are kept from shearing the firstlings of the sheep, we should not act openly too quickly, even if we have begun some solid work. Since our life begins as something simple and innocuous, it is proper that we should not lay aside the covering of its privacy, lest it show itself naked to human eyes once the wool has been sheared. The firstlings of cattle and sheep are suitable only for divine sacrifices. Whatever we begin with that is strong, simple and innocent, we should offer on the altar of our hearts to the honor of the secret judge. And he without a doubt receives it more gladly if it has been hidden from men and not stained with any desire for praise. But often the beginnings of a new conversion are mixed with elements of a carnal life and hence should not become known too quickly. Otherwise, when the good that is acceptable is praised, the soul is deceived by praise and cannot grasp the evils that still lie concealed in it.

Every firstborn born in your cows or your sheep, if you are male, you will consecrate it to the Lord your God. It is necessary to investigate if those who in Greek are called protótoka and in Latin can only be called "firstborn" (firstborn) are only those born of mothers, since these creatures properly are rather delivered than not generated. In fact, giving birth corresponds in Greek to tíktein, which is an act of the female -where protothokon is derived-; engendering, on the other hand, corresponds to gennan, so in Latin it is properly called "firstborn." Well, of the females the first ones were born, that is to say, the creatures that were born the first ones, not those that were engendered the first by the husbands, in the case that they were engendered of widowed women, who had already given birth . Because otherwise it would not be these creatures that would open the maternal womb, a fact on which the law of those who were born first and who were to be consecrated to the Lord is properly based. Now, if in these words there is a certain distinction, then it is not said in vain that the Lord is not monotonous; (only born) of the Father, but monogenés -ie, only begotten, because he is unique-; but in Latin it is certainly said to be the firstborn among the dead, (Col 1,18) because the Latin word can not be composed in that way, according to our way of speaking; in Greek, on the other hand, it is said prototokos (first born) and not protogenic (first begotten), as if the Father had begotten one equal to himself, and, on the other hand, the creature would have given birth to him. The text that says: Firstborn of all creation (Col 1,15), where the Greek word protótokos also appears, can be understood according to the new creation, about which the Apostle says: If, then, it is in Christ a new creation (2Co 5,17). Christ is the first of this creation, because the first rose not to die again, and so that death does not dominate again (Cf Rm 6,9), something that is promised to be so at last for the new creation that takes place in it. But this distinction can not be stated recklessly, but must be investigated more diligently in the Scriptures. Because it draws attention how it could be said in the Proverbs: Firstborn, I tell you, son (Pv 24,70 31,2), that is, of what person is meant to be said. If it refers to Christ as said by the person of God the Father -…