Islam is pretty tricky if you don't have a decent background in the Gospel. One man always asks to show one place where Jesus claimed to be God. He says he will convert to Christianity if you can. Of course, he knows it is not possible because Jesus openly said he would not use self-witness.
John 5:31
If I bear witness of myself, my witness is not true.
So, Jesus refused to self-witness as his authority. Muslim's know this and know there are few statements of Christ bragging on his nature. Jesus rejected self-witness but said there are true witnesses. The first was John the Baptist. Satan is smart in asking for self-witness statements because he knew Jesus wouldn't stoop to such. Jesus simply let others, including his Father, bear witness.
John 5:32
There is another that beareth witness of me; and I know that the witness which he witnesseth of me is true.
John 5:33
Ye sent unto John, and he bare witness unto the truth.
When they asked John about Jesus John confirmed Jesus was the messiah and he witnessed the Spirit descend upon Jesus. Yet, Jesus said that wasn't good enough. Jesus would not rely on any man.John's testimony was able to convince men to salvation, but wasn't the definitive witness
John 5:41
I receive not honour from men.
The true and best witness was the Father himself. It was the only witness that was necessary in the eyes of Christ.
Muslims miss this point, the Father himself confirmed Jesus was the Son of God, and God in nature. Muslims reject the Fathers witness that was revealed in works and scripture. Jesus declared those rejecting the Father's witness do not have a true love of God.
John 5:36
But I have greater witness than [that] of John: for the works which the Father hath given me to finish, the same works that I do, bear witness of me, that the Father hath sent me.
John 5:37
And the Father himself, which hath sent me, hath borne witness of me. Ye have neither heard his voice at any time, nor seen his shape.
Jesus declares the Father bore witness to Jesus is works and in Scripture. Scripture is inspired of God and scripture declares
Heb.1:5-8
unto the Son he says, thy throne O God is forever and ever
So, Islam rejects the witness of the Father.
Psalms 2:7
I will tell of the decree: The Lord said to me, "you are my Son, this day have I begotten