Be Peace Be Upon You All 
Why Should Believe In The Final Prophet Muhammad (Peace Be Upon Him) ???
In the Quran we learn that the final prophet will be prophesied in the previous revelations
Quran 5:157
“Those who follow the Messenger, the unlettered prophet, whom they find written in what they have of the Torah and the Gospel”
In the Bible there are numeral prophecies of the final prophet to come. However due to limitation of time and space I only wish to focus on the prophecies Jesus pbuh gave, after a brief introduction from the Torah.
The Jewish Rabi’s (Scholars) ask John the following, based on their knowledge of the Torah:
In John 1:18-22 they ask John the following:
1. Are you the Christ, he says "No" !
2. Are you Elijah, he says "No" !
3. Are you THAT PROPHET, he says "No" !
We know that John was Elijah (as later appointed), and that he was not the Christ (that is 3-2=1).
They knew based on their scripture (Old Testament) there are three messengers of God to come. So who is THAT PROPHET they are referring to ?
Even Jesus (Peace Be Upon Him) speaks about “THAT PROPHET”:
John 14:16 Jesus pbuh says; then I will pray to my Father to send you another comforter.
(another comforter, meaning another of whomever he is; a “son of man”, a prophet of God, as prophets were classified as 'son of man' Ezekiel 12:2).
Further if we read, John 15:26 says, "And when I pray to my father and He sends you another comforter, he will abide with you forever.
John 16:7 nevertheless I tell you the truth, it is important for you that I GO AWAY for if I GO NOT AWAY the comforter shall not come, but if I depart shall I send him.
Only once Jesus pbuh leaves will another comforter come! Thus we know that this prophecy cannot refer to the Holy Spirit since the Holy Spirit has been there during the Gospel of Jesus pbuh and in the Old Testiment, for instance:
It came upon Joshua pbuh
It came upon David pbuh
It came upon the Jews to guide them to safety as a cloud during the day and a flame at night (God cannot be seen John 5:37)
It came upon Simpson (to give him strength), who was not a prophet
It was even there during the time of Jesus pbuh in the Gospel and helped him and the disciples.
Thus this cannot be the Holy Spirit Jesus pbuh is prophesying about.
John 16:12-14 Jesus pbuh says; I have many things to say unto you, but I can not bear them now, for he when the spirit of truth shall come he shall guide you on to all truth. He shall not speak of himself, all he hear shall he speak, he shall show you things to come, he shall glorify me.
Now Lets analyze This Prophecy !
We already know that this prophecy does not refer to the Holy Spirit, but who is this person then ?
**For he ** (meaning someone):
1. "He shall not speak of himself":
Mohammad pbuh never speaks of himself in the Quran.
2. "All that he hears he will speak":
All that prophet Mohammad pbuh heard he spoke.
3. "He shall show you many things to come":
The Quran shows us many things we only discover today due to advanced science and technology, as well as signs of the last days. Of the 6236 verses in the Quran more than 1000 speak about recent established science (a miracle from God).
4. "He shall glorify me":
Mohammad pbuh spoke highly of Jesus pbuh. The Quran and the Hadith of the prophet speaks about Jesus pbuh as one of the mightiest prophets of God.
This prophecy does not befit anyone better than the last and final messenger of Almighty God, prophet Mohammad PBUH.
So my Christian friends, what I learned from the Bible about Islam, I just explain :).
May God Almighty Give Us Hidaya To Be On Straight Path Before Doomsday !
Ameen
Stay Blessed All !!!