On the Allegories of the Sacred Laws (2.33-2.37)

It is necessary therefore, that every created thing should at times be changed. For this is a property of every created thing, just as it is an attribute of God to be unchangeable. But of these beings who have been changed, some remain in their altered state till their final and complete destruction, though others are only exposed to the ordinary vicissitudes of human nature; and they are immediately preserved.

On which account Moses says that God will not suffer the destroyer to enter into your houses to smite them.[*] For he does permit the destroyer (and change is the destruction of the soul) to enter into the soul, in order to exhibit the peculiar characteristic of the created being. But God will not permit the offspring of the seeing Israel to be changed in such a manner as to be stricken down by the change; but he will compel it to emerge and rise up again like one who rises up from the deep, and so he will cause it to be saved.

He took one of his ribs. He took one of the many powers of the mind, namely, that power which dwells in the outward senses. And when he uses the expression, He took, we are not to understand it as if he had said, He took away, but rather as equivalent to He counted, He examined; as he says in another place, Take the chief of the spoils of the captivity.[*] What, then, is it which he wishes to show?

Sensation is spoken of in a twofold manner; —the one kind being according to habit, which exists even when we are asleep, and the other being according to energy. Now, in the former kind, the one according to habit, there is no use: for we do not comprehend any one of the objects presented to our view by its means. But there is use in the second, in that which exists according to energy; for it is by means of this that we arrive at a comprehension of the objects perceptible by the outward senses.

Accordingly, God, having created the former kind of sensation, that existing according to habit, when he was creating the mind (for he was furnishing that with many faculties in a state of rest), desires now to complete the other kind which exists according to energy. And this one according to energy is perfected when the one which exists according to habit is put in motion, and extended as far as the flesh and the organs