John Gill

But I said unto you,.... The substance of what follows in Joh 6:26 though the Persic and Ethiopic versions render it, "I say unto you"; and so refers not to anything before said, but to what he was about to say: that ye also have seen me, and believe not; that is, they had not only seen him in person, which many kings, prophets, and righteous men had desired, but not enjoyed, yet nevertheless believed; but they had seen his miracles, and had shared in the advantages of them, being healed, and fed corporeally by him, and yet believed not in him as the spiritual Saviour and Redeemer of their souls; nor did they come to him in a spiritual way, for eternal life and salvation.