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We repeatedly say that Jesus Christ, peace be upon him, is a Muslim; whereupon, Christians laugh sarcastically, asking: "When did he embrace Islam?"
I will tell you when; but first of all do you know what Islam is?
Islam means submission and surrender to the Will of Allah the Almighty , Exalted be His Name. It is bearing witness that there is no god but Allah and believing in His Messengers. That is Islam. This is what Prophet Muhammad, peace be upon him, called for: i.e., bearing witness that there is no god but Allah and that Muhammad is the Messenger of Allah and submitting and surrendering to the Will of Allah. All Prophets have this in common; i.e., the origin of the Creed which is the Oneness (Monotheism) of Allah (God) and submission to the Will of Allah.
They differed only in the laws; in legislation. Any human being, since the beginning of creation - who believed in the Oneness of Allah, the One and Only who has no partner; and believed in His Messengers and followed His orders and prohibitions - is a Muslim; because he submitted and surrendered  to the Will  of  Allah the Almighty. 

Jesus Christ says:
"Now this is eternal life: that they know you, the only true God, and Jesus Christ, whom you have sent." John 17: 3
He says: "that they know you"; i.e., to believe in you; to bear witness...
"the only true God"; i.e., there is no god but Allah...
" and Jesus Christ, whom you have sent" ; i.e., Jesus Christ , the Messenger of Allah.
Thus, the Christ calls for bearing witness that there is no god but Allah and that Jesus Christ is the Messenger of Allah.
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It is Islam , O' Christians ...
Now, what is your Judgment of Jesus Christ?
Is he infidel  or apostate?!!!!!
For he called his followers to submit their wills to the Will of Allah (God); as he says: 

"For I have come down from heaven not to do my will but to do the will of him who sent me." John 6: 38 
And this is the essence of Islam: Submission of one's will to the Will of Allah (God).

⬅️ Do you like the Christ?
“If you love me, keep my commands." John 14: 15
So, what are these commands?
Jesus replied, "The most important commandment is this: 'Listen, O Israel! The LORD our God is the one and only LORD." Mark 12: 29
"Right, Teacher, the scribe replied.“You have stated correctly that God is One and there is no other but Him" Mark 12: 32.

"The LORD our God is the one and only LORD." (Mark 12: 29) This is the speech of Jesus Christ himself. Do you see, he does not call for trinity. He disagrees with the Christians of today .... why?!!! Because he called for absolute Oneness of God ... "The LORD our God is the one and only LORD." He did not say that the first and most important commandment is that I am your god the son and there is god the father. He did not say that the first commandment is that god is one in a trinity; father, son, and holy spirit and that he is the second Person in the trinity, ... etc., of this sick creed. No, no, he never said this. Rather, he said like Muslims, "The LORD our God is the one and only LORD" where is the word 'trinity?' No where. Where did he say: 'I am god, worship me'?