To help a Muslim understand better the title “Son of God” I suggest the following:
If you think that it is blasphemy to say that God had close personal relations with Mary and so produced the Son of God, then we agree with you. So how is the description “the Son of God” meant to be understood?
If a book is called “the mother of books”, for say Italian cooking, does it mean that all other Italian cook books came from that one book? No. It means that this book is considered the best source of information for Italian cooking.
Does the phrase “a son of the road” mean that two roads got together and produced another road? No. It is an expression meaning that a person is a traveller.
The same principle applies to the description of “the Son of God.” Jesus Christ eternally was the Son of God as seen in Isaiah 9:6 “For unto us a child us born, unto us a son is given…” and 1John 4:14″And we have seen and do testify that the Father sent the Son to be the Saviour of the world.” As someone had to exist before they are sent anywhere, so Jesus Christ was eternally in the character of the Son of God before He was also sent to the earth and became a Man. “Jesus Christ the same yesterday, and today and forever.” (Hebrews 13:8) (DP)