Gerhard quoting Athanasius:
Athanasius, Contra Arian., sermon 3: “It is unseemly to ask how the Word is from God or how the splendor of God exists or how God begets or what the manner of the begetting of God is. He who would dare such things is crazy because with words he is trying to explain something indescribable, something proper to the divine nature and known only to God and His Son.”
Gerhard, Johann Theological Commonplaces: Exegesis IV on Christ, 18