The earliest none Islamic sources are as early as 2 years after his given death, references:
Doctrina Jacobi (July 634)
................ I, having arrived at Sykamina, stopped by a certain old man well-versed in scriptures, and I said to him: "What can you tell me about the prophet who has appeared with the Saracens?" He replied, groaning deeply: "He is false, for the prophets do not come armed with a sword. ........ (Doctrina Jacobi V.16, 209. [p. 57])
Sophronius, Patriarch of Jerusalem (d. ca. 639)
Well dear RevertedRevert that Jacobi guy who talked to some Christian/Jewish guy who must be describing a rogue that was wandering as Muhammad .,
"A... Muhammad " .."A ..LEADER "..
A leader of bandits and thugs
[In a synodical letter without date, Sophronius gives an extensive list of heretics and asks, in the valedictions, that the following may be granted by God to "our Christ-loving and most gentle emperors":]
a strong and vigorous sceptre to break the pride of all the barbarians, and especially of the Saracens who, on account of our sins, have now risen up against us unexpectedly and ravage all with cruel and feral design, with impious and godless audacity. More than ever, therefore, we entreat your Holiness to make urgent petitions to Christ so that he, receiving these favourably from you, may quickly quell their mad insolence and deliver these vile creatures, as before, to be the footstool of our God-given emperors. (Ep. synodica, PG 87, 3197D-3200A [p. 69])
[The following comments are dated to December of 634.]
We, however, because of our innumerable sins and serious misdemeanours, are unable to see these things, and are prevented from entering Bethlehem by way of the road. Unwillingly, indeed, contrary to our wishes, we are required to stay at home, not bound closely by bodily bonds, but bound by fear of the Saracens. (Christmas Sermon, 506 [p. 70])
At once that of the Philistines, so now the army of the godless Saracens has captured the divine Bethlehem and bars our passage there, threatening slaughter and destruction if we leave this holy city and dare to approach our beloved and sacred Bethlehem. (Christmas Sermon, 507 [p. 70])
If we were to live as is dear and pleasing to God, we would rejoice over the fall of the Saracen enemy and observe their near ruin and witness their final demise. For their blood-loving blade will enter their hearts, their bow will be broken and their arrows will be fixed in them. (Christmas Sermon, 515 [p. 71])
ALL THAT IS NOTHING TO DO WITH ORIGINAL MUHAMMAD PREACHER
[This dates to the 6th of December in 636 or 637.]
But the present circumstances are forcing me to think differently about our way of life, for why are [so many] wars being fought among us? Why do barbarian raids abound? Why are the troops of the Saracens attacking us? Why has there been so much destruction and plunder? Why are there incessant outpourings of human blood? Why are the birds of the sky devouring human bodies? Why have churches been pulled down? Why is the cross mocked? Why is Christ, who is the dispenser of all good things and the provider of this joyousness of ours, blasphemed by pagan mouths (ethnikois tois stomasi) so that he justly cries out to us: "Because of you my name is blasphemed among the pagans," and this is the worst of all the terrible things that are happening to us. That is why the vengeful and God-hating Saracens, the abomination of desolation clearly foretold to us by the prophets, overrun the places which are not allowed to them, plunder cities, devastate fields, burn down villages, set on fire the holy churches, overturn the sacred monasteries, oppose the Byzantine armies arrayed against them, and in fighting raise up the trophies [of war] and add victory to victory. Moreover, they are raised up more and more against us and increase their blasphemy of Christ and the church, and utter wicked blasphemies against God. Those God-fighters boast of prevailing over all, assiduously and unrestrainably imitating their leader, who is the devil, and emulating his vanity because of which he has been expelled from heaven and been assigned to the gloomy shades. Yet these vile ones would not have accomplished this nor seized such a degree of power as to do and utter lawlessly all these things, unless we had first insulted the gift [of baptism] and first defiled the purification, and in this way grieved Christ, the giver of gifts, and prompted him to be angry with us, good though he is and though he takes no pleasure in evil, being the fount of kindness and not wishing to behold the ruin and destruction of men. We are ourselves, in truth, responsible for all these things and no word will be found for our defence. What word or place will be given us for our defence when we have taken all these gifts from him, befouled them and defiled everything with our vile actions? (Holy Baptism, 166-167 [pp. 72-73])
[In a work originally composed by John Moschus (d. 619), but expanded by Sophronius (d. ca. 639), actually found only in an addition of the Georgian translation, the following entry appears, concerning a construction dated by tradition at 638, i.e., soon after the capture of Jerusalem ca. 637. It appears in a portion concerning Sophronius as recounted on the authority of his contemporary, the archdeacon Theodore, and may have been written down ca. 670.]
the godless Saracens entered the holy city of Christ our Lord, Jerusalem, with the permission of God and in punishment for our negligence, which is considerable, and immediately proceeded in haste to the place which is called the Capitol. They took with them men, some by force, others by their own will, in order to clean that place and to build that cursed thing, intended for their prayer and which they call a mosque (midzgitha). (Pratum spirituale, 100-102 [p. 63])
AG 945, indiction VII: On Friday, 4 February, [i.e., 634 CE / Dhul Qa‘dah 12 AH] at the ninth hour, there was a battle between the Romans and the Arabs of Mụhammad [Syr. tayyāyē d-Ṃhmt] in Palestine twelve miles east of Gaza. The Romans fled, leaving behind the patrician YRDN (Syr. BRYRDN), whom the Arabs killed. Some 4000 poor villagers of Palestine were killed there, Christians, Jews and Samaritans. The Arabs ravaged the whole region.
AG 947, indiction IX: The Arabs invaded the whole of Syria and went down to Persia and conquered it; the Arabs climbed mountain of Mardin and killed many monks there in [the monasteries of] Kedar and Benōthō. There died the blessed man Simon, doorkeeper of Qedar, brother of Thomas the priest
Now In that quotes ., it says
" On Friday, 4 February, [i.e., 634 CE / Dhul Qa‘dah 12 AH] at the ninth hour, there was a battle between the Romans and the Arabs of Mụhammad"THE LAST MUHAMMAD.. A LEADER..... DIED IN THE YEAR 632 CE., So 634 CE MUHAMMAD WAS ANOTHER LEADER ANOTHER IMPOSTOR dear RevertedRevert
Seberos, around 660:
At that time a certain man from along those same sons of Ismael, whose name was Mahmet [i.e., Mụhammad], a merchant, as if by God's command appeared to them as a preacher [and] the path of truth. He taught them to recognize the God of Abraham, especially because he was learnt and informed in the history of Moses. Now because the command was from on high, at a single order they all came together in unity of religion. Abandoning their vain cults, they turned to the living God who had appeared to their father Abraham. So, Mahmet legislated for them: not to eat carrion, not to drink wine, not to speak falsely, and not to engage in fornication. He said: 'With an oath God promised this land to Abraham and his seed after him for ever. And he brought about as he promised during that time while he loved Ismael. But now you are the sons of Abraham and God is accomplishing his promise to Abraham and his seed for you. Love sincerely only the God of Abraham, and go and seize the land which God gave to your father Abraham. No one will be able to resist you in battle, because God is with you.
Nothing to do with "Muhammad " that is described in Quran....
Topic: Was Muhammed an Epileptic ?