11 Lo, again, another question is made clear:— We enquire in what tongues our Lord gave the power of speaking to the dumb, who from all tongues came unto Him? And although this be easy to know, yet our soul impels us to that knowledge which is greater than this. That [knowledge] then is, to know that through the Son the first man was made. For in this fact, that through Him speech was given to the dumb, the sons of Adam, we may learn that through Him speech was given to Adam their first father.
And here also defective nature was supplied by our Lord. He, then, Who was able to supply the defect of nature,— it is manifest that through Him is established the supplying of nature. But there is no greater defect than this, when a man is born without speech. For since it is in this, in speech, that we excel all the creatures, the defect of it is greater than all [other] defects. He, then, through Whom all this defect was supplied—it is manifest that through Him all fullness is established.
But because through Him the members receive all fullness in the womb secretly, through Him their defect was supplied openly; that we might learn that through Him in the beginning the whole frame was constituted. He spat then on His fingers and placed them in the ears of that deaf man; and He mixed clay of His spittle, and spread it upon the eyes of the blind man; that we might learn that as there was defect in the eyeballs of that man who was blind from his mother's womb, so there was defect in the ears of this [man].
So then, by leaven from the body of Him Who completes, the defect of our formation is supplied. For it was not meet that our Lord should have cut off anything from His body to supply the deficiency of other bodies; but with that which could be taken away from Him, He supplied the deficiency of them that lacked; just as in that which can be eaten, mortals eat Him. He supplied then the deficiency, and gave life to mortality, that we may know that from the body in which fullness dwelt, the deficiency of them that lacked was supplied; and from the body in which life dwelt, life was given to mortals.
Source: On Our Lord (New Advent)