As Muslims, the first and foremost thing that makes us Muslims is to testify and believe in these lines:
I testify that there is no god worthy of worship but Allah
And Muhammad is his messenger
The second line means a lot more than just what is translated however, and as Muslims we believe that Muhammad is "khaatim al-anbiyaa" which means "the seal of all prophets." He is the last prophet to be sent, which is evident in both the Quran and ahadeeth (sayings of the prophet) which means to say otherwise is to doubt the word of God and he word of his apostle, which is the only truth.
Ghulam Ahmad came out at a time when the British were trying to take over India, and they needed someone to stop the Muslims from fighting, and so bribed this man to assist them. While undertaking this task, he claimed himself to be many things:
- a mujaddid (which is someone that comes to a nation every century after hijrah to return Islam to its original beliefs after being changed or forgotten)
- Imam al-Mahdi
- the promised messiah (Jesus)
- a prophet
But these claims are easily proven false:
- He could not have been a mujaddid as he definitely was not correcting Islam, and so was disregarded by scholars of that time.
- He could not have been imam mahdi, as he didn't fit the descriptions of the promised mahdi (i.e Muhammed pbuh told us a man will be born towards the end of time, and he will be born into a life exactly like our prophet, and this man wasn't -- he was born in India, with a mom and dad of completely different names to our prophet, etc.)
- He could not have been Jesus as he definitely did not fit the descriptions of Jesus (i.e. he had a father, his name definitely wasn't Issa (Jesus), etc.)
- He could not have been a prophet as there are over 70 ahadeeth regarding the finality of our prophet, as well as quranic verses.
One of the main ahadeeth that will help is the following:
There will arise 30 impostors in my ummah and each one of them will pronounce to the world that he is a prophet, but I am the last in line of the prophets of God and no prophet will come after me.
Jami` at-Tirmidhi, 2219
In-book reference: Book 33, Hadith 62
English translation: Vol. 4, Book 7, Hadith 2219
This man is obviously one of those men. Also in another hadeeth, our prophet states that the day of judgement will not occur until 30 one-eyed liars will come and claim to be a prophet of God. "One-eyed liars" refers to those who resemble the dajjal, as they will have one eye "bulging like a grapefruit." Take a look at Ahmad's picture and you'll see what I mean.
Our prophet has also stated that Islam will be divided into 73 sects, and only one will enter paradise:
"The Jews were divided into 71 sects, one of which is in Paradise and 70 are in the fire. The Christians were divided into 72 sects, 71 of which are in the fire and one is in paradise. By the one in whose hand is the soul of Muhammad, my ummah will be divided into 73 sects, one of which will be in paradise and 72 will be in the Fire." It was said, O Messenger of Allah, who are they? He said, "Al-Jamaa'ah."
Sunan Ibn Majah, 3992
In-book reference: Book 36, Hadith 67
English translation: Vol. 5, Book 36, Hadith 3992
Al-Jamaa'ah is that which follows the Quran and his Sunnah (his way of life). How can someone who disregards God's word and follow a prophet after Mohammed be a Muslim? And how can they call themselves Muslim if they disregard our prophet and follow another man who claims to be a prophet? If he really was a prophet, where is his book, where are his teachings? And if he really is a prophet, he wouldn't have died in a toilet.
This is only a summary of what I know about this man and the people who follow him, as I have completed a whole assignment on him and can provide a lot more evidence as to why he is not Muslim, and neither are those who follow him, but Allah knows best, and only He can judge us all.
May Allah guide us all to the right path, Amen.