Translated by Allan Menzies.
2. How the Prophets and Holy Men of the Old Testament Knew the Things of Christ.
"And this is the witness of John."  This is the second recorded testimony of John the Baptist to Christ. The first begins with "This was He of whom I said, He that cometh after me," and goes down to "The only-begotten Son of God who is in the bosom of the Father, He hath declared him." Heracleon supposes the words, "No one has seen God at any time," etc., to have been spoken, not by the Baptist, but by the disciple. But in this he is not sound. He himself allows the words, "Of his fulness we all received, and grace for grace; for the law was given by Moses, but grace and truth came by Jesus Christ," to have been spoken by the Baptist. And does it not follow that the person who received of the fulness of Christ, and a second grace in addition to that he had before, and who declared the law to have been given by Moses, but grace and truth to have come through Jesus Christ, is it not clear that this is the person who understood, from what he received from the fulness of Christ, how "no one hath seen God at any time," and how "the only-begotten who is in the bosom of the Father" had delivered the declaration about God to him and to all those who had received of His fulness? He was not declaring here for the first time Him that is in the bosom of the Father, as if there had never before been any one fit to receive what he told His Apostles. Does he not teach us that he was before Abraham, and that Abraham rejoiced and was glad to see his day? The words "Of his fulness all we received," and "Grace for grace," show, as we have already made clear, that the prophets also received their gift from the fulness of Christ and received a second grace in place of that they had before; for they also, led by the Spirit, advanced from the introduction they had in types to the vision of truth. Hence not all the prophets, but many of them,  desired to see the things, which the Apostles saw.
 John i. 19.
 Matt. xiii. 17.
Reference address : https://www.ellopos.net/elpenor/greek-texts/fathers/origen/john-commentary.asp?pg=126