Passages such as the following make it sound like the Prophet Muhammad thought the Christian Trinity was comprised of God, Mary, and their offspring Jesus:
God will say: ‘Jesus Son of Mary, did you ever say to mankind: “Worship me and my mother as gods besides God?”’
‘Glory be to you,’ he will answer, ‘I could never have claimed what I have no right to.’ (5.117)
The Creator of the heavens and the earth—how should he have a son, seeing that He has no consort, and He created all things? (6.102)