First of all, it is clear that Allah States in the Qur’an that one can be a Muslim but also be a non believer at the same time. Allah States:
The Arabs of the desert say, ‘We believe.’ Say, “You have not believed yet; but rather say, ‘We have accepted Islam,’ for the true belief has not yet entered into your hearts.” But if you obey Allah and His Messenger, He will not detract anything from your deeds Surely, Allah is Most Forgiving, Merciful.(Chapter 49 Verse 15)
A hadith relating to the same ayah mentioned above states:
أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ الأَعْلَى، قَالَ حَدَّثَنَا مُحَمَّدٌ، – وَهُوَ ابْنُ ثَوْرٍ – قَالَ مَعْمَرٌ وَأَخْبَرَنِي الزُّهْرِيُّ، عَنْ عَامِرِ بْنِ سَعْدِ بْنِ أَبِي وَقَّاصٍ، عَنْ أَبِيهِ، قَالَ أَعْطَى النَّبِيُّ صلى الله عليه وسلم رِجَالاً وَلَمْ يُعْطِ رَجُلاً مِنْهُمْ شَيْئًا قَالَ سَعْدٌ يَا رَسُولَ اللَّهِ أَعْطَيْتَ فُلاَنًا وَفُلاَنًا وَلَمْ تُعْطِ فُلاَنًا شَيْئًا وَهُوَ مُؤْمِنٌ . فَقَالَ النَّبِيُّ صلى الله عليه وسلم ” أَوْ مُسْلِمٌ ” . حَتَّى أَعَادَهَا سَعْدٌ ثَلاَثًا وَالنَّبِيُّ صلى الله عليه وسلم يَقُولُ ” أَوْ مُسْلِمٌ ” . ثُمَّ قَالَ النَّبِيُّ صلى الله عليه وسلم ” إِنِّي لأُعْطِي رِجَالاً وَأَدَعُ مَنْ هُوَ أَحَبُّ إِلَىَّ مِنْهُمْ لاَ أُعْطِيهِ شَيْئًا مَخَافَةَ أَنْ يُكَبُّوا فِي النَّارِ عَلَى وُجُوهِهِمْ ” .
It was narrated from ‘Amir bin Sa’d bin Abi Waqqas that his father said:
“The Prophet [SAW] gave a share (of some spoils of war) to some men and not to others. Sa’d said: ‘O Messenger of Allah [SAW], you gave to so-and-so and so-and-so, but you did not give anything to so-and-so, and he is a believer.’ The Prophet [SAW] said: ‘Or a Muslim,’ until Sa’d had repeated it three times, and the Prophet [SAW] said: ‘I give to some men, and leave those who are dearer to me, without giving them anything, lest (the former) be thrown into Hell on their faces.'”(Sunan An Nasai, Volume 6, Book 47, Hadith #4995)
And:
أَخْبَرَنَا عَمْرُو بْنُ مَنْصُورٍ، قَالَ حَدَّثَنَا هِشَامُ بْنُ عَبْدِ الْمَلِكِ، قَالَ حَدَّثَنَا سَلاَّمُ بْنُ أَبِي مُطِيعٍ، قَالَ سَمِعْتُ مَعْمَرًا، عَنِ الزُّهْرِيِّ، عَنْ عَامِرِ بْنِ سَعْدٍ، عَنْ سَعْدٍ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَسَمَ قَسْمًا فَأَعْطَى نَاسًا وَمَنَعَ آخَرِينَ فَقُلْتُ يَا رَسُولَ اللَّهِ أَعْطَيْتَ فُلاَنًا وَمَنَعْتَ فُلاَنًا وَهُوَ مُؤْمِنٌ . قَالَ ” لاَ تَقُلْ مُؤْمِنٌ وَقُلْ مُسْلِمٌ ” . قَالَ ابْنُ شِهَابٍ { قَالَتِ الأَعْرَابُ آمَنَّا } .
It was narrated from Sa’d that :
The Messenger of Allah [SAW] distributed (some spoils of war) and gave to some people but withheld from others. I said: “O Messenger of Allah, you gave to so-and-so and so-and-so, and you withheld from so-and-so, who is a beliver.” He said: “Do not say ‘a believer,’ say ‘a Muslim.'” Ibn Shihab (one of the narrators) said: The Bedouins say: “We believe”.(Sunan An Nasai, Volume 6, Book 47, Hadith #4996)
The Holy Prophet(saw) has beautifully explained similar of a person being a disbeliever within Islam in this hadith:
حَدَّثَنَا آدَمُ، حَدَّثَنَا شُعْبَةُ، عَنِ الأَعْمَشِ، عَنْ ذَكْوَانَ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم “ لاَ يَزْنِي الزَّانِي حِينَ يَزْنِي وَهْوَ مُؤْمِنٌ، وَلاَ يَسْرِقُ حِينَ يَسْرِقُ وَهْوَ مُؤْمِنٌ، وَلاَ يَشْرَبُ حِينَ يَشْرَبُهَا وَهْوَ مُؤْمِنٌ، وَالتَّوْبَةُ مَعْرُوضَةٌ بَعْدُ ”.
Narrated Abu Huraira: The Prophet (ﷺ) said, “The one who commits an illegal sexual intercourse is not a believer at the time of committing illegal sexual intercourse and a thief is not a believer at the time of committing theft and a drinker of alcoholic drink is not a believer at the time of drinking. Yet, (the gate of) repentance is open thereafter.”(Sahih Bukhari Volume 8, Book 82, Hadith 801)
Promised Messiah(as) never called other Muslims kaffir.He always called them his Muslim brothers if you take a look at his writings,and always treated them with respect.
Ahmad(As) said:
“He who does not call us a kafir, we do not call him a kafir at all.”
“We do not declare anyone to be outside Islam unless he himself becomes a kafir by calling us kafirs. It is not perhaps known to you that when I first claimed to have been appointed by God, Maulvi Abu Said Muhammad Husain of Batala prepared a fatwa with great effort in which it was written that I was a kafir, etc. ..Now it is accepted on all hands that anyone who calls a believer a kafir himself becomes a kafir”
Non Ahmadi’s usually bring a quote from a letter to Dr Hakim, but this is in detail explained by Promised Son(ra) and was actually a reply to people who call the Messiah(as) kaffir. They were not even the words of the Messiah(As) rather a revelation from Allah to him. If you read the whole reply he who does not accept me is not general to all rather apply to those ulama who had declared Ahmad(As) and Ahmadis as kafir.
Also the Promised Son, Hazrat Mirza Bashiruddin Mahmood Ahmad(Ra) beautifully explained the status of Non Ahmadi Muslims although many of his statements are misinterpreted. He(ra) states:
“There is a lot of difference in the definition of kufr between Ahmadis and non-Ahmadis. They consider the meaning of Kafir to be denial of Islam, but we do not give it this meaning for them.”
“We believe that after a certain point, a man gets the right of calling himself a Muslim, but when he denigrates from that point, he can be called a Muslim but not a true Muslim. This is our definition of Kufr and Islam.”
“According to this definition, we do not say that every kafir will go to hell for eternity. We do not even say that for Jews and Christians. We believe one day God will free them from Hell and they will enter paradise.”
“Again I pronounce that we do not give kufr the meaning which they (other Muslims) give. According to our meaning, when a person considers Islam as his religion and Qur’anic commandments as his manual for life, he gets the right of being called Muslim but in the true sense he only becomes Muslim when he acts upon the Islamic teachings. However, when he denies some fundamental principle of Islam then he is called Muslim but in the true sense does not remain Muslim.”
“We do not say someone is kafir in the meaning that he is rejecting Hadrat Muhammad (sa) as a prophet, when some say that I believe in Hadrat Muhammad (sa), then who can say that you do not? In our opinion, denying of fundamentals of Islam is kufr and such a person cannot be a TRUE Muslim.”
Hazrat Mirza Tahir Ahmad(ra) stated:
“The opposite of a believer, is a disbeliever, and the opposite of a Muslim is a non Muslim and in these two things God has placed a difference– For God says [to the Holy Prophet(saw)] Tell them God, Who is the Knower of the Unseen, has given me the knowledge that belief has not yet entered in your hearts. Therefore, do not claim to be believers, but we do not take away your right to call yourselves Muslims”
You are still a Muslim but not a true Muslim.You have committed disbelief by rejecting the Promised Messiah(As) in not only him, but the prophecies of Muhammad(saw) as well.
This is commonly misunderstood with many Non Ahmadis. For some reason they believe that as Ahmadis we say that they are non Muslims and this is totally incorrect.There are different types of kufr (disbelief). There are some types of kufr which do not make you a non Muslim rather are kufr within Islam. Here is a example from the Ahadith :
حَدَّثَنَا يَحْيَى بْنُ يَحْيَى التَّمِيمِيُّ، وَعُثْمَانُ بْنُ أَبِي شَيْبَةَ، كِلاَهُمَا عَنْ جَرِيرٍ، قَالَ يَحْيَى أَخْبَرَنَا جَرِيرٌ، عَنِ الأَعْمَشِ، عَنْ أَبِي سُفْيَانَ، قَالَ سَمِعْتُ جَابِرًا، يَقُولُ سَمِعْتُ النَّبِيَّ صلى الله عليه وسلم يَقُولُ “ إِنَّ بَيْنَ الرَّجُلِ وَبَيْنَ الشِّرْكِ وَالْكُفْرِ تَرْكَ الصَّلاَةِ ” .
It is narrated on the authority of Jabir that he heard the Apostle (may peace and blessings be upon him) saying. Verily between man and between polytheism and unbelief is the negligence of prayer.( : Sahih Muslim 82 a) Skipping prayer is also a form of kufr according to this authentic narration, but does not make you a non Muslim.
If you follow these conditions, no one has a right to declare you a non Muslim:
حَدَّثَنَا عَمْرُو بْنُ عَبَّاسٍ، قَالَ حَدَّثَنَا ابْنُ الْمَهْدِيِّ، قَالَ حَدَّثَنَا مَنْصُورُ بْنُ سَعْدٍ، عَنْ مَيْمُونِ بْنِ سِيَاهٍ، عَنْ أَنَسِ بْنِ مَالِكٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم “ مَنْ صَلَّى صَلاَتَنَا، وَاسْتَقْبَلَ قِبْلَتَنَا، وَأَكَلَ ذَبِيحَتَنَا، فَذَلِكَ الْمُسْلِمُ الَّذِي لَهُ ذِمَّةُ اللَّهِ وَذِمَّةُ رَسُولِهِ، فَلاَ تُخْفِرُوا اللَّهَ فِي ذِمَّتِهِ ”.
Narrated Anas bin Malik:
Allah’s Messenger (ﷺ) said, “Whoever prays like us and faces our Qibla and eats our slaughtered animals is a Muslim and is under Allah’s and His Apostle’s protection. So do not betray Allah by betraying those who are in His protection.” (Bukhari, Vol. 1, Book 8, Hadith 386)
Ahmad(As) is a prophet of Allah and is the same messiah(As) whom the Prophet Muhammad(Saw) had prophesied about. If you reject Ahmad(As) you are not rejecting him alone, but rather are rejecting Muhammad(Saw) as well because it was him who made the prophecies which were all accepted.By rejecting Hadhrat Mirza Ghulam Ahmad(As) you have committed kufr in him and in reality have also went against the prophecies of Muhammad(Saw) the Seal of all the Prophets and committed disbelief in regards to his prophecies about the Messiah(As). Non Ahmadi Muslims are indeed Muslims but it is clear that they are not true Muslims.
Some also quote a saying where Ahmad(as) has stated that those who oppose him are opposing Muhammad(saw) and are jahanami. There is nothing wrong with this statement and whoever raises this allegation has no clue of the Ahadith of the Holy Prophet Muhammad(saw). He(saw) stated:
حَدَّثَنَا مَحْمُودُ بْنُ غَيْلاَنَ، حَدَّثَنَا أَبُو دَاوُدَ الْحَفَرِيُّ، عَنْ سُفْيَانَ الثَّوْرِيِّ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ زِيَادِ بْنِ أَنْعُمَ الإِفْرِيقِيِّ، عَنْ عَبْدِ اللَّهِ بْنِ يَزِيدَ، عَنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم “ لَيَأْتِيَنَّ عَلَى أُمَّتِي مَا أَتَى عَلَى بَنِي إِسْرَائِيلَ حَذْوَ النَّعْلِ بِالنَّعْلِ حَتَّى إِنْ كَانَ مِنْهُمْ مَنْ أَتَى أُمَّهُ عَلاَنِيَةً لَكَانَ فِي أُمَّتِي مَنْ يَصْنَعُ ذَلِكَ وَإِنَّ بَنِي إِسْرَائِيلَ تَفَرَّقَتْ عَلَى ثِنْتَيْنِ وَسَبْعِينَ مِلَّةً وَتَفْتَرِقُ أُمَّتِي عَلَى ثَلاَثٍ وَسَبْعِينَ مِلَّةً كُلُّهُمْ فِي النَّارِ إِلاَّ مِلَّةً وَاحِدَةً قَالُوا وَمَنْ هِيَ يَا رَسُولَ اللَّهِ قَالَ مَا أَنَا عَلَيْهِ وَأَصْحَابِي ” . قَالَ أَبُو عِيسَى هَذَا حَدِيثٌ مُفَسَّرٌ حَسَنٌ غَرِيبٌ لاَ نَعْرِفُهُ مِثْلَ هَذَا إِلاَّ مِنْ هَذَا الْوَجْهِ .
Narrated ‘Abdullah bin ‘Amr:
that the Messenger of Allah (ﷺ) said: “What befell the children of Isra’il will befall my Ummah, step by step, such that if there was one who had intercourse with his mother in the open, then there would be someone from my Ummah who would do that. Indeed the children of Isra’il split into seventy-two sects, and my Ummah will split into seventy-three sects. All of them are in the Fire Except one sect.” He said: “And which is it O Messenger of Allah?” He said: “What I am upon and my Companions.(Jami’at Tirmidhi #2641)
This does not mean that all of these sects would be non Muslims rather shows they would be misguided, as are the ones who reject Ahmad(as).