18 Is not this like that which we read in the Gospel? For we praise the power of the same Author in each case, nor does it be a work or a gift, since He confers a gift in His works, and works in His gift. For that which He gave to others to be done, this His Name effects in the work of others. So we read in the Gospel, that the Jews, when they saw the gift of healing in the blind man, called for the testimony of his parents, and asked: “How does your son see?” when he said: “Whereas I was blind, now I see.” And in this case the man says, “I was blind and now I see.” Ask others if you do not believe me; ask strangers if you think his parents are in collusion with me. The obstinacy of these men is more hateful than that of the Jews, for the latter, when they doubted, at least asked his parents; the others enquire in secret and deny in public, incredulous not as to the work, but as to its Author.
Source: Letters (New Advent)