|Detail from an ancient Syrian icon of Pentecost.
The following is excerpted from my book, Facing Islam, pp 101-106, slightly reformatted, with new topic headings. Sections 4 and 5 have been added for this presentation. (Updated 6/17/19, 8:07am.)
Parakletos, not Periklytos -
The One to Come is the Holy Spirit, not a False Prophet from Arabia
1. Manuscript Evidence
|Fragment p75 of the Bodmer Papyrus,
showing John 14:9-26a,
with the Greek word “Parakletos”
in verses 16 and 26.
Muslim attempts to prove that Muhammad was prophesied by Jesus as the “messenger to come” are typically based on these passages in the Gospel According to St John:
“And I will pray the Father, and He will give you another Helper [Greek: Parakletos], that He may abide with you forever” (Jn 14:16).
“Nevertheless I tell you the truth. It is to your advantage that I go away; for if I do not go away, the Helper [Greek: Parakletos] will not come to you; but if I depart, I will send Him to you” (Jn 16:7).
Muslim apologists would have us believe that the New Testament was corrupted so as to eradicate the prophecies about Muhammad. They claim that the true Greek word in these verses should be Periklytos, not Parakletos. Periklytos may be translated as “glorious,” so Muslims argue that it refers to Muhammad (spoken of in Sura 61:6 as Ahmad), whose name means “the praised [or glorious] one.”
This is of course absurd, but it is educational for us to turn to the actual manuscript evidence, which is undeniable. There are, in fact, over seventy existing Greek manuscripts of the New Testament, all of which date from well before the time of Muhammad, and all of which prove that the original Greek word used in John 14:16, 14:26 and 16:7 is Parakletos. Two of the oldest manuscripts, Codex Sinaiticus (mid 4th c.) and Codex Alexandrinus (late 4th or early 5th c.) are actually housed in the British Museum in London and may be examined. The oldest complete manuscript of the New Testament, Codex Vaticanus (early 4th c.) likewise confirms the use of Parakletos in these verses. The even more ancient Bodmer Papyrus fragment of St. John’s Gospel (ca. 200 A.D.) also verifies the use of Parakletos in Chapter 14: 16, 26.
Even Fr. Theodore Pulcini in his booklet Face To Face writes strongly against the Islamic doctrine of tahriff, providing us an apt summary of our discussion of both the Old and New Testament manuscript evidence:
Anyone who has studied the manuscripts of the Jewish and Christian scriptures knows there is no evidence whatever for the corruption posited by the doctrine of tahriff. In fact the manuscript evidence, if it establishes anything, establishes how carefully the texts of the Old and New Testaments were passed down.
2. He cannot be a man.
Beyond the physical manuscript evidence, we note that the coming of the Holy Spirit is prophesied by name all through the Gospels and in Acts (eg., Jn 1:33, Jn 7:39, Mt 28:19, Acts 1:4-5). He quite clearly cannot be a man. He — the Holy Spirit, the Parakletos — is a Someone far greater with a specific ministry and mission. In the context of St. John’s Gospel alone we see this quite clearly:
He is not a mere human person:
“He will abide with you forever” (Jn 14:16).
“He will be the Spirit of Truth” (Jn 14:17).
“He dwells with you and will abide in you” (Jn 14:17).
He will testify to Jesus Christ:
“The Father will send [Him] in My [Jesus’] name” (Jn 14:26).
“[He] will remind you of everything I have said to you” (Jn 14:26).
“He will glorify Me” (Jn 16:14).
Conclusively, in one single verse the person of the Holy Spirit is specifically identified as the Parakletos, the Helper:
“But the Helper [Parakletos], the Holy Spirit, Whom the Father will send in My Name, He will teach you all things, and bring to your remembrance all things I have said to you” (Jn 14:26).
Decisively, the universal witness of the Church from the days of Christ to the present testifies to the correct understanding of just who is the Helper, the Parakletos. And, as we know, since the Holy Spirit glorifies Jesus Christ and takes of what is Christ’s and makes it known to His disciples, therefore any teacher or “prophet” who denies Jesus Christ, who goes against the revelation given by Christ, who disputes or contradicts the teachings of Christ—all of which is embodied and lived by the Orthodox Church—is of the spirit of antichrist.
St. Gregory Palamas made the same point in the form of a rhetorical question in repudiating his Muslim captors:
The Evangelist says, “Every spirit that does not confess that Jesus Christ has come in the flesh is not of God” (1 Jn 4:3a). How shall we accept a book [the Koran] that says there shall come one [Muhammad] from God, who is not actually the Lord, when the Evangelist declares, that one is not from God, if he does not confess that Jesus, Who has come in the flesh, is the Lord? This is not possible to do—no it is not. (Patriarch Philotheos Kokkinos, The Life of Gregory Palamas, p. 369.)
St. Gregory does not cite the last portion of 1 Jn 4:3 (“This is the spirit of Antichrist”), but his point is emphatically made.
The Apostle Paul likewise counters this spirit and speaks prophetically to the claims of Muhammad in his second letter to the Corinthians, where he repudiates false apostles:
But what I do, I will also continue to do, that I may cut off the opportunity from those who desire an opportunity to be regarded just as we are in the things of which they boast. For such are false apostles, deceitful workers, transforming themselves into apostles of Christ. And no wonder! For Satan himself transforms himself into an angel of light. Therefore it is no great thing if his ministers also transform themselves into ministers of righteousness, whose end will be according to their works (2 Cor 11:12-15).
3. The Apostolic Witness
In condemning those whom he sarcastically calls ‘super apostles’, St Paul condemns Muhammad (and all like him), whose motives are not pure, not love of God and neighbor, but who rather abuse others and exalt themselves so as to profit:
For you put up with fools gladly, since you yourselves are wise! For you put up with it if one brings you into bondage, if one devours you, if one takes from you, if one exalts himself, if one strikes you on the face (2 Cor 11:19-20).
We must not be reluctant to assert that the strongest proof against Muslim claims that either (1) Muhammad was prophesied about in the Old or New Testaments, or (2) the Hebrews and Christians deliberately distorted their scriptures thus expunging the Islamic teaching, is the integrity of the Apostolic witness, which translates into the very continuity of the living witness of the Mind of Christ, the mind of the Fathers, the mind of the Holy Orthodox Church.
Holy Tradition, which we know to be the life of the Holy Spirit within the Church, knows nowhere of any teaching of “a Prophet” to arise after Christ. True prophets have arisen and will continue to be born from within the womb of the Church, but these are believers in Jesus Christ, inspired by the Holy Spirit, and the witness of their holy life and Orthodox faith testifies that they are true followers of Jesus Christ and worthy to be heard.
4. The Lord's Own Words
Per the Lord's words, a false prophet will always be rejected by the true flock:
"Truly, truly, I say to you, he who does not enter the sheepfold by the door but climbs in by another way, that man is a thief and a robber. But he who enters by the door is the shepherd of the sheep. To him the gatekeeper opens.
"The sheep hear his voice, and he calls his own sheep by name and leads them out. When he has brought out all his own, he goes before them, and the sheep follow him, for they know his voice. A stranger they will not follow, but they will flee from him, for they do not know the voice of strangers...
"Truly, truly, I say to you, I am the door of the sheep. All who came before me are thieves and robbers, but the sheep did not listen to them. I am the door. If anyone enters by me, he will be saved and will go in and out and find pasture. The thief comes only to steal and kill and destroy. I came that they may have life and have it abundantly. I am the good shepherd. The good shepherd lays down his life for the sheep."
John 10:1-5, 7-11
5. Confusing Christ with Belial... er, Muhammad
Those Christians who are inclined to make peace with the religion of Muhammad, who consider Muhammad to be a true "apostle and man of God", and who seek to reassure us that Islam is in harmony with Christianity , or that the Allah of Islam is the same as the True God we worship in the Orthodox Church  have confused Christ with Belial, Jesus with Muhammad, Light with darkness, Truth with lies.
Such Christians are false shepherds, false disciples, and thieves, who will only steal, kill and destroy the flock.
There can be no fellowship of Christ with Muhammad, nor of Truth with falsehood. All who say otherwise are either tempted by or in outright deception from the spirit of antichrist:
Beloved, believe not every spirit, but try the spirits whether they are of God: because many false prophets are gone out into the world.
Hereby know ye the Spirit of God: Every spirit that confesseth that Jesus Christ is come in the flesh is of God, and every spirit that confesseth not that Jesus Christ is come in the flesh is not of God; and this is the spirit of antichrist, whereof ye have heard that it should come, and even now already is it in the world.
1 John 4:1-3
Muhammad and his Koran emphatically deny Jesus Christ and the Blessed Trinity. How otherwise can one understand these rantings, direct quotes from the Koran?
The similitude of Isa [Jesus] before God is as that of Adam; He created him from dust, then said to him: “Be”: And he was. (Sura 3:59)
Say not “Trinity”: desist: It will be better for you: For God is One God: Glory be to Him: (Far Exalted is He) above having a son. . . . (Sura 4:173)
In blasphemy indeed are those that say that God is Christ the Son of Mary. (Sura 5:19)
They do blaspheme who say: “God is Christ the son of Mary . . .” They do blaspheme who say: God is one of three in a Trinity: for there is no god except One God. If they desist not from their word (of blasphemy), verily a grievous penalty will befall the blasphemers among them (Sura 5:75,78)
Christ the son of Mary was no more than an Apostle; many were the apostles that passed away before him. His mother was a woman of truth. They had both to eat their (daily) food. See how God doth make His Signs clear to them; yet see in what ways they are deluded away from the truth! (Sura 5:78)
The Jews call 'Uzair a son of God, and the Christians call Christ the Son of God. That is a saying from their mouth; (in this) they but imitate what the Unbelievers of old used to say. God's curse be on them: how they are deluded away from the Truth! (Sura 9:30)
In fact, they never killed him, they never crucified him — they were made to think that they did. All factions who are disputing in this matter are full of doubt concerning this issue. They possess no knowledge; they only conjecture. For certain, they never killed him. (Sura 4:157)
Orthodox Christians, do not be deceived. Islam is a false religion, Muhammad a false prophet, tools of the ages old enemy of mankind, that serpent who slithered in the Garden at the beginning, who seeks now to lure as many Orthodox Christians away from Jesus Christ as possible, some through embracing Muhammad as a true prophet and Islam as akin to Christianity.
We must reject Islam and Muhammad, yet at the same time, we must remember that the sign of a Christian is love. We must always be prepared to witness to Jesus Christ by our words and our life, and be likewise prepared to invite Muslims to repent of their falsehood and come to the Light, the saving knowledge of the True God through His Divine Son, Jesus Christ.
 "The Prophet Muhammad is an apostle, He is a man of God, who worked for the Kingdom of God... When I speak against Islam, then I am not found in agreement with God." - Patriarch Parthenius of Alexandria (Orthodoxos Typos 854, May 1982)
 "I am completely sure that if you are a Christian and you know a lot about Islam and love what you know, your heart will embrace the Muslims around you and if you are educated, you will hold in esteem much from their religion and openly recognize the truth that is in their religion." - Met. Georges Khodr (Source)
 "Muslims and Christians worship the same God." - Fr Theodore Pulcini, Face To Face, Light & Life Publishing, 2008, p1.