The Quran Verse:
Surah 6:101
[He is] Originator of the heavens and the earth. How could He have a son when He does not have a companion and He created all things? And He is, of all things, Knowing.
The Relevant Source Text (Christian Orthodox Doctrine):
John 1:1 and 1:14:
In the beginning was the Word, and the Word was with God, and the Word was God... And the Word became flesh and dwelt among us, and we have seen his glory, glory as of the only Son from the Father, full of grace and truth.
The Quran attempts to refute the Christian belief that Jesus is the Son of God, but it does so using a logical fallacy based on pagan biology. The Quran asks, "How could God have a son without a wife/companion?"
To a Christian scholar, this proves the Quranic author possessed a grossly physical, anthropomorphic misunderstanding of Christian theology.
Historic Christianity has NEVER taught that God the Father took a physical wife and reproduced sexually to create Jesus. "Son of God" is a relational and spiritual title denoting that Jesus is the eternal Word (Logos) radiating from the Father.
By arguing against a physical, sexual reproduction that Christians do not even believe in, the Quran attacks a strawman, demonstrating a human author's ignorance of the very faith he is trying to debunk.