In The Name of Allaah, The Most Merciful, The Bestower of Mercy.

Imaam As-Sadi [may Allaah have mercy upon him] said:

And among the people are those who believe in some of the Messengers and the divine Books, but not in the other Messengers and divine books, even though the Messengers and the divine Books affirmed the truthfulness of each other, agreed with each other, and were in agreement in the fundamental principles. So, their denial invalidated their belief, and their acknowledgment of some of the Prophets and the divine books became invalidated by their denial of the other Prophets and divine books; so they remained in deviation in their religion, bewildered in their faith and in a state of contradiction in their knowledge. Allaah [The Exalted] said:

إن الذين يكفرون بالله ورسله ويريدون أن يفرقوا بين الله ورسله ويقولون نؤمن ببعض ونكفر ببعض ويريدون أن يتخذوا بين ذلك سبيلا أولئك هم الكافرون حقا

Verily, those who disbelieve in Allah and His Messengers and wish to make distinction between Allah and His Messengers (by believing in Allah and disbelieving in His Messengers) saying, “We believe in some but reject others,” and wish to adopt a way in between. They are in truth disbelievers. [Surah An-Nisaa. Aayaat 150-151]

So, Allaah passed a judgment of disbelief against them because He knows that their claim to belief was incorrect, and if it was true, they would have believed in all the facts on which the Messengers agreed, but (Allaah said) that they said: [نؤمن بما أنزل علينا ويكفرون بما وراءه وهو الحق مصدقا لما معهم – “We believe in what was sent down to us”. And they disbelieve in that which came after it, while it is the truth confirming what is with them]. [Surah Al-Baqarah. Aayah 91]  That is why their claim of faith is a false claim, so Allaah [The Exalted and Majestic] said about them: [فلم تقتلون أنبياء الله من قبل إن كنتم مؤمنين – Why then have you killed the Prophets of Allah aforetime, if you indeed have been believers?]

Commentary:

This is another solution adopted by the diseased intellects in the subject matter of faith, religion and creed, and that is amongst the people are those who believe in some of the Messengers and the divine books, but they do not believe in the other Messengers and divine books, even though the Messengers and books confirm the truthfulness of each other and agreed with each other in the fundamental principles, as the Prophet [peace and blessings of Allaah be upon him] said, “The Prophets are (like) paternal brothers, their mothers are different, but their religion is one”.(1)

“The Prophets are (like) paternal brothers” – Meaning, the creed and fundamental principles of the Prophet was one. There was difference in the creed of the Prophets, and this why the scholars have stated that the sound creed of the Prophets can never be abrogated. The creed of all the Prophets- the first to the last of them – was one creed; but difference only occurred in the different laws given to them (which is the meaning of the statement, “their mothers are different”. Allaah said: [لِكُلٍّ۬ جَعَلۡنَا مِنكُمۡ شِرۡعَةً۬ وَمِنۡهَاجً۬ا‌ۚ – To each among you, We have prescribed a law and a clear way.] [Surah Al-Maa’idah. Aayah 48] (see footnote a)

This is why belying some of the Prophets or some of Allaah’s divine books is tantamount to be belying all the Prophets and divine books. Allaah stated about the people of Prophet Nooh: [كَذَّبَتۡ قَوۡمُ نُوحٍ ٱلۡمُرۡسَلِينَ – The people of Nooh belied the Messengers. (Surah Ash-Shu’araa. Aayah 105)] They only belied Nooh, but belying one Prophet is tantamount to belying all the Prophets because the creed of all the Prophets is one.

So, after the author clarified the corruption of the polytheists (refer to part 4 of this series), he then clarified the corruption of those who claim ascription to some of the religions, such as the Jews -those who claim that they are followers of Prophet Musa [peace be upon him], and the Christians- those who claim that they are followers of Prophet Isa [peace be upon him]; but they disbelieve in Muhammad [peace and blessings of Allaah be upon him] and the message he was sent with. Imaam Ibnul Qayyim [may Allaah have mercy mercy upon him] mentioned a discussion that took place between him and a Christian (as follows):

Ibnul Qayyim said to the Christian, “You have insulted the Lord (i.e. Allaah) of entire existence in a manner that none amongst the creation has done before you.”

The Christian replied, “May God forbid that is the case”.

Ibnul Qayyim said to him, “In your statement that Muhammad is a false Prophet, there is insult against the Lord of the entire existence in a manner that none of the creation has uttered before you”.

The Christian said, “How is that the case?”

Ibnul Qayyim said, “From the time Allaah sent Muhammad, his religion has not ceased being elevated and none has attempted to confront this religion, except that his affair became lowly (inferior). Allaah said:

[هُوَ ٱلَّذِىٓ أَرۡسَلَ رَسُولَهُ ۥ بِٱلۡهُدَىٰ وَدِينِ ٱلۡحَقِّ لِيُظۡهِرَهُ ۥ عَلَى ٱلدِّينِ ڪُلِّهِ – It is He (Allaah) Who has sent His Messenger (Muhammad ) with guidance and the religion of truth (Islam), to make it superior over all religions] [Surah At-Tawbah. Aayah 33)]

Therefore, either Allaah knows about it or does not know. If you say that Allah does not know, then you have insulted Allaah in a manner that none has insulted Him; but if you say that Allaah knows about it, then Allaah has stated:

وَلَوۡ تَقَوَّلَ عَلَيۡنَا بَعۡضَ ٱلۡأَقَاوِيلِ
لَأَخَذۡنَا مِنۡهُ بِٱلۡيَمِينِ
ثُمَّ لَقَطَعۡنَا مِنۡهُ ٱلۡوَتِينَ
فَمَا مِنكُم مِّنۡ أَحَدٍ عَنۡهُ حَـٰجِزِينَ

And if he (Muhammad ) had forged a false saying concerning Us (Allah), We surely should have seized him by his right hand (or with power and might), and then certainly should have cut off his life artery (Aorta), and none of you could withhold Us from (punishing) him. [Surah Al-Haaqqah. Aayaat 44-47]

The Christian said, “God forbid that we say he is a false prophet; rather he is a true prophet and our sensible people say that he is a truthful Prophet and his followers are people of success (in this life and the next)”.

Ibnul Qayyim said to him, “What stops you from becoming one of his followers?”

The Christian said, “Musa is also a truthful prophet and Isa is a truthful prophet, and I am one of the followers of Isa”.

Ibnul Qayyim said to him, “If you say that he (Muhammad) is a truthful prophet and you do not believe in him, then indeed he has declared the one who does not believe in him a disbeliever, and that such a person is an inhabitant of the fire. He said, ‘By the one in whose hand is the soul of Muhammad, none from this nation of Jews and Christians hears of me, and then dies without having faith in my message, but that he will be an inhabitant of Hellfire’. (2) Therefore, either you say that he is truthful prophet and follow him, so that you are from the people who are successful and saved, or you negate this claim with your actions”.

The Christian said, “Speak to be about something else other than this topic”. So, the Christian sought to escape from the subject matter.

Allaah said:

إِنَّ ٱلَّذِينَ يَكۡفُرُونَ بِٱللَّهِ وَرُسُلِهِۦ وَيُرِيدُونَ أَن يُفَرِّقُواْ بَيۡنَ ٱللَّهِ وَرُسُلِهِۦ وَيَقُولُونَ نُؤۡمِنُ بِبَعۡضٍ۬ وَنَڪۡفُرُ بِبَعۡضٍ۬ وَيُرِيدُونَ أَن يَتَّخِذُواْ بَيۡنَ ذَٲلِكَ سَبِيلاً
أُوْلَـٰٓٮِٕكَ هُمُ ٱلۡكَـٰفِرُونَ حَقًّ۬ا‌ۚ

Verily, those who disbelieve in Allah and His Messengers and wish to make distinction between Allah and His Messengers (by believing in Allah and disbelieving in His Messengers) saying, “We believe in some but reject others,” and wish to adopt a way in between. They are in truth disbelievers. [Surah An-Nisaa. Aayah 150-151]

So, this is one of the corrupt solutions in the subject matter of creed (i.e. belief in some Prophets and divine books and disbelief in others). The first corrupt solution was that of the polytheists (refer to part 4 of this series) and the second is that of ahlul kitaab (i.e. those Jews and Christians who deviated from the path of their prophets). [Source: https://www.al-badr.net/detail/UY7sjBcaQE from 45mins 38secs to 58mins 50secs. paraphrased]

Ref 1: Saheeh Al-Bukhaaree. Number 3443

Footnote a: Imaam As-Sadi [may Allaah have mercy upon him] said in his explanation of the statement:

[لِكُلٍّ۬ جَعَلۡنَا مِنكُمۡ شِرۡعَةً۬ وَمِنۡهَاجً۬ا‌ۚ – To each among you, We have prescribed a law and a clear way.] [Surah Al-Maa’idah. Aayah 48] These divine laws that differed in different communities of the Prophets are the ones that Allaah changed according to the change of time and circumstances, and all of them were based on justice when they were legislated. As for the major fundamental principles which will always be (a necessary) means of wellbeing and are always based on wisdom in all eras, they remain the same and were legislated in all the different laws of the Prophets. [refer to article for more detail: https://salaficentre.com/2020/01/27/allaahs-commands-are-applicable-in-every-era-and-place-tawheed-salaah-zakaat-kind-treatment-towards-parents-orphans-and-the-poor-utter-good-speech/

[Ref 2: Ṣaḥeeh Muslim 153]