The big disagreement

The Christians and Muslims don't  agree on this issue. The issue is God.

The Muslims believe there is no god but Allah-the God. And they deny the trinity.

The bible teaches this. One God is revealed in Scripture as Father, Son and Holy Spirit.
Within the one essence of the Godhead, there are three persons who are coequally and co-eternally God.

Matthew 13:13-17

 

¹³ This is why I speak to them in parables:

“Though seeing, they do not see;
    though hearing, they do not hear or understand.

¹⁴ In them is fulfilled the prophecy of Isaiah:

“‘You will be ever hearing but never understanding;
    you will be ever seeing but never perceiving.
¹⁵ For this people’s heart has become calloused;
    they hardly hear with their ears,
    and they have closed their eyes.
Otherwise they might see with their eyes,
    hear with their ears,
    understand with their hearts
and turn, and I would heal them.’

¹⁶ But blessed are your eyes because they see, and your ears because they hear. ¹⁷ For truly I tell you, many prophets and righteous people longed to see what you see but did not see it, and to hear what you hear but did not hear it.

Matthew 28:19

 Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit,

 

 

2 Corinthians 13:14

  May the grace of the Lord Jesus Christ, and the love of God, and the fellowship of the Holy Spirit be with you all.