Since the world began - Neither Moses nor any of the prophets had ever done this. No instance of this kind is recorded in the Old Testament. As this was a miracle which had never been performed, the man argued justly that he who had done it must be from God. As Jesus did it not by surgical operations, but by clay, it showed that he had power of working miracles by any means. It may be also remarked that the restoration of sight to the blind by surgical operations was never performed until the year 1728. Dr. Cheselden, an English surgeon, was the first who attempted it successfully, who was enabled to remove a cataract from the eye of a young man, and to restore sight. This fact shows the difficulty of the operation when the most skillful natural means are employed, and the greatness of the miracle performed by the Saviour.

Since the world began - Εκ του αιωνος, From the age - probably meaning from the commencement of time. Neither Moses nor the prophets have ever opened the eyes of a man who was born blind: if this person then were not the best of beings, would God grant him a privilege which he has hitherto denied to his choicest favorites?
Opened the eyes of one that was born blind - It will readily appear that our Lord performed no surgical operation in this cure: the man was born blind, and he was restored to sight by the power of God; the simple means used could have had no effect in the cure; the miracle is therefore complete. That there are cases, in which a person who was born blind may be restored to sight by surgical means, we know: but no such means were used by Christ: and it is worthy of remark that, from the foundation of the world, no person born blind has been restored to sight, even by surgical operation, till about the year of our Lord, 1728; when the celebrated Dr. Cheselden, by couching the eyes of a young man, 14 years of age, who had been born blind, restored him to perfect soundness. This was the effect of well directed surgery: that performed by Christ was a miracle.

Since the world began,.... , "from eternity", or never: the phrase answers to frequently used by the Jews (m), for never; and so the Arabic version renders it, "it was never heard", &c. since time was:
was it not heard, that any man opened the eyes of one that was born blind; as not any physician by any natural means, or art, so not any prophet in a miraculous way, no not Moses himself; among all the miracles he wrought, which the Jews say (n) were seventy six, and which were two more than were wrought by all the prophets put together, this is not to be found in the list of them, nor in the catalogue of miracles done by others. Elisha indeed prayed to God to restore sight to an army smitten with blindness; but then they were persons who saw before, and were not blind from their birth. Wherefore it must follow, that Jesus, the author of this miracle, must be greater than any of the prophets, even than Moses himself, and has a greater confirmation of his mission from God, than either he or they had: and as this was a miracle in nature, it is no less a miracle in grace, that one born in the blindness and darkness of sin, ignorance, and infidelity, should have the eyes of his understanding opened, to behold divine and spiritual things.
(m) Abot R. Nathan, c. 35. fol. 8. 2. Maimon. Mechira, c. 20. sect. 8. & Shelchim & Shotaphim, c. 10. sect. 1, 2, 3, 4. & passim. (n) Menasseh ben lsrael, Conciliat. in Deut. Quaest. 11. p. 240.