1 For the Lord, revealing Himself to His disciples, that He Himself is the Word, who imparts knowledge of the Father, and reproving the Jews, who imagined that they, had [the knowledge of] God, while they nevertheless rejected His Word, through whom God is made known, declared, “No man knows the Son, but the Father; neither knows any man the Father, save the Son, and he to whom the Son has willed to reveal [Him].” Thus has Matthew set it down, and Luke in like manner, and Mark the very same; for John omits this passage. They, however, who would be wiser than the apostles, write [the verse] in the following manner: “No man knew the Father, but the Son; nor the Son, but the Father, and he to whom the Son has willed to reveal [Him];” and they explain it as if the true God were known to none prior to our Lord's advent; and that God who was announced by the prophets, they allege not to be the Father of Christ.
Source: Adversus haereses (New Advent)