Heraclcon asserts, that this is a declaration of the disciple, not of the Baptist: an unreasonable supposition; for if the words, Of His fulness have we all received, are the Baptist’s, does not the connexion run naturally, that he receiving of the grace of Christ, the second in the place of the first grace, and confessing that the law was given by Moses, but grace and truth came by Jesus Christ; understood here that no man had seen God at any time, and that the Only Begotten, who was in the bosom of the Father, had committed this declaration of Himself to John, and all who with him had received of His fulness? For John was not the first who declared Him; for He Himself who was before Abraham, tells us, that Abraham rejoiced to see His glory.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: in Joan. t. vi. §. 2