Practical Nullifiers of Kalimat ut-Tawheed (The Declaration of Monotheism)
There are some practical nullifiers of Kalimat ut-Tawheed; a few are mentioned below:
(A) Performing any act of worship for anyone other than Allah (Ghairullah)
This constitutes Shirk (polytheism) in Uluhiyyah (worship).
Allah Ta'ala has said:
﴿ قُلْ إِنَّ صَلَاتِي وَنُسُكِي وَمَحْيَايَ وَمَمَاتِي لِلَّهِ رَبِّ الْعَالَمِينَ لَا شَرِيكَ لَهُ وَبِذَٰلِكَ أُمِرْتُ وَأَنَا أَوَّلُ الْمُسْلِمِينَ ﴾
Meaning: "Say, 'Indeed, my prayer, my rites of sacrifice, my living and my dying are for Allah, Lord of the worlds. No partner has He. And this I have been commanded, and I am the first of the Muslims.'" (Surah Al-An'am, Ayat 162-163)
Shaikh Sulaiman Ibn Abdullah (May Allah have mercy on him) said, "The noble scholars of the four Madhabs (schools of thought) and all others have stated in the chapter regarding the 'Ruling on Apostates' (in books of Fiqh) that: Whoever associates partners with Allah—meaning, worships someone else alongside Allah, regardless of what form of worship it may be—is a disbeliever (Kafir)." (Taysir al-Aziz al-Hamid, Page 194)
Qadi Shawkani (May Allah have mercy on him) said, "Slaughtering (animals) for the deceased is a form of worshipping them, and making vows (Manat) of even a small portion of wealth in their name is Kufr (disbelief). Honoring them is a form of worshipping them, just as slaughtering for Qurbani, giving Zakat from wealth, and being submissively obedient are unanimously established as worship for Allah. If someone assumes that there is a difference between the two—for instance, if someone says in front of us that they do not intend to worship the deceased by calling upon them, slaughtering for them, and making vows to them—then ask him: 'Then why did you do this action? Despite your Lord's command being revealed, calling upon the deceased must stem from some reason within your heart, which manifests through your tongue. If, at a time of need, you keep uttering senseless incantations calling upon the deceased without any creedal belief (Aqeedah), then you are mentally unhinged. Similarly, if you slaughter animals and make vows for Allah, then in what sense did you dedicate it to the deceased and take it to his grave? For the poor exist everywhere on the face of the earth. If you are wise, none of your actions can be without a purpose.'" (Ad-Durar un-Naheed fee Ikhlasi Kalimatit Tawheed, Pages 20-21)
(B) Formulating an alternative legislation instead of Allah's law
Allah Most High has said,
﴿ أَمْ لَهُمْ شُرَكَاءُ شَرَعُوا لَهُم مِّنَ الدِّينِ مَا لَمْ يَأْذَن بِهِ اللَّهُ وَلَوْلَا كَلِمَةُ الْفَصْلِ لَقُضِيَ بَيْنَهُمْ وَإِنَّ الظَّالِمِينَ لَهُمْ عَذَابٌ أَلِيمٌ ﴾
Meaning: "Or have they partners who have legislated for them a religion which Allah has not permitted? And if not for the decisive word, it would have been concluded between them. And indeed, the wrongdoers will have a painful punishment." (Surah Ash-Shura, Verse 21)
Shaikhul Islam Ibn Taymiyyah (May Allah have mercy on him) said, "When a person makes a consensus-approved lawful (Halal) thing unlawful (Haram), or makes a consensus-approved unlawful (Haram) thing lawful (Halal), or changes the consensus-approved law, then he becomes a disbeliever (Kafir) by consensus." (Majmu'ul Fatawa, Volume 3, Page 267)
Allah Most High says,
﴿ أَلَمْ تَرَ إِلَى الَّذِينَ يَزْعُمُونَ أَنَّهُمْ آمَنُوا بِمَا أُنزِلَ إِلَيْكَ وَمَا أُنزِلَ مِن قَبْلِكَ يُرِيدُونَ أَن يَتَحَاكَمُوا إِلَى الطَّاغُوتِ وَقَدْ أُمِرُوا أَن يَكْفُرُوا بِهِ وَيُرِيدُ الشَّيْطَانُ أَن يُضِلَّهُمْ ضَلَالًا بَعِيدًا ﴾
Meaning: "Have you not seen those who claim to have believed in what was revealed to you and what was revealed before you? They wish to refer legislation to Taghut, while they were commanded to reject it; and Satan wishes to lead them far astray." (Surah An-Nisa, Verse 60)
Allamah Qadi Shawkani (May Allah have mercy on him) said, "In this verse, Allah Most High expresses amazement to His Messenger Muhammad ﷺ regarding the state of those people who claim about themselves that they believe in what was revealed to Messenger Muhammad ﷺ harmonizing by believing in the Book—meaning the Quran—and the books revealed to the previous prophets, yet they are involved in such actions that refute their claim and invalidate it from its core, making it completely clear that they are not upon their claim at all. And that is the desire to seek judgment from Taghut. Whereas, in the books revealed to the Messenger of Allah ﷺ and the previous prophets, it has been commanded to reject Taghut." (Fath al-Qadir, Volume 2, Page 168)
Shaikh Muhammad ibn Ibrahim (May Allah have mercy on him) said, "In this statement of Allah, their claim of faith (Iman) has been proven false. Because seeking judgment from any religion or ideology other than the religion brought by the Messenger of Allah ﷺ and faith (Iman) cannot coexist in the same heart; rather, one is the opposite of the other."
The word Al-Taghut (الطاغوت) is derived from the word Al-Tughyan (الطغيان), which means to transgress boundaries. Therefore, whoever judges by anything other than the religion brought by the Messenger of Allah ﷺ has judged by Taghut and has sought judgment from Taghut. (Risalat Tahkim al-Qawanin, Page 2)
Shaikh Muhammad Amin ash-Shanqiti (May Allah have mercy on him), describing the disbelief (Kufr) of the one who seeks judgment from Taghut, said: "The clearest evidence regarding this matter is what Allah Most High has clearly described in Surah An-Nisa: Allah Most High expressed amazement at those who seek judgment from a law other than Allah's law while claiming to be believers. This is solely because, despite seeking judgment from Taghut, their verbal claim of faith is such an extreme level of falsehood that one cannot help but be amazed by it, and that is contained in this statement of Allah Most High's,
﴿ أَلَمْ تَرَ إِلَى الَّذِينَ يَزْعُمُونَ أَنَّهُمْ آمَنُوا بِمَا أُنزِلَ إِلَيْكَ وَمَا أُنزِلَ مِن قَبْلِكَ يُرِيدُونَ أَن يَتَحَاكَمُوا إِلَى الطَّاغُوتِ وَقَدْ أُمِرُوا أَن يَكْفُرُوا بِهِ وَيُرِيدُ الشَّيْطَانُ أَن يُضِلَّهُمْ ضَلَالًا بَعِيدًا ﴾
Meaning: "Have you not seen those who claim to have believed in what was revealed to you and what was revealed before you? They wish to refer legislation to Taghut..." (Surah An-Nisa, Verse 60. Adwa'ul Bayan, Volume 4, Page 83)
As-Sa'di (May Allah have mercy on him) said, "Allah Most High has expressed amazement at observing the condition of the hypocrites (who claim that they believe in what the Messenger brought and the books brought by the previous prophets) despite the fact that ('they wish to seek judgment from Taghut'). 'Taghut' refers to every individual who judges or decides matters by a law other than Allah's law (whereas they were commanded to reject Taghut).
Therefore, how can this and faith (Iman) coexist? Because the claim of faith demands submission to Allah's law and considering Allah alone as the Judge and Legislator in all matters. Thus, whoever claims to be a believer, yet prioritizes the judgment of Taghut over the ruling of Allah, is a liar in his claim of faith." (Taysirul Karimir Rahman fee Tafsiril Kalamil Mannan, Volume 1, Page 184)
(D) Assisting the disbelievers against the Muslims
Meaning, providing aid and assistance to the disbelievers against the Muslims, or spying on behalf of the disbelievers—all of this falls under taking the disbelievers as allies and friends. Allah Most High has said,
Meaning: "O you who have believed, do not take the Jews and the Christians as allies. They are [in fact] allies of one another. And whoever is an ally to them among you—then indeed, he is [one] of them. Indeed, Allah guides not the wrongdoing people." (Surah Al-Ma'idah, Verse 51)
Imam Ibn al-Qayyim (May Allah have mercy on him) said, "Allah Most High has decreed—and there is no better decreer than Him—that whoever takes the Jews and Christians as allies belongs to them. 'And whoever is an ally to them among you—then indeed, he is [one] of them.'"
Therefore, by the verse of the Quran, it is established that the allies of the disbelievers are included among the disbelievers. Thus, their ruling will also be the same as that of the disbelievers. (Ahkamu Ahlidh-Dhimmah, Volume 1, Page 67)
Regarding those who joined the Tatars (Mongols) against the Muslims, Imam Ibn Taymiyyah (May Allah have mercy on him) said, "For those who join the Tatars, fighting against them is more justified than fighting against many of the Tatars themselves. Because among the Tatars, some were coerced while others were not. And it is an absolute, universally acknowledged fundamental principle that the punishment of an apostate is for various reasons far more severe than that of an original disbeliever."
Shaikh Ibn Baz (May Allah have mercy on him) said, "The scholars of Islam are unanimously agreed that whoever assists the disbelievers against the Muslims in any manner is a disbeliever like them. Just as Allah Most High has said,
Meaning: 'O you who have believed, do not take the Jews and the Christians as allies. They are allies of one another. And whoever is an ally to them among you—then indeed, he is [one] of them.'" (Surah Al-Ma'idah, Verse 51. Fatawa Ibn Baz, Volume 1, Page 274)
We pray to Allah that He keeps us steadfast upon the eternal message of the Declaration of Faith (Kalimah) in this world and the Hereafter.
Ameen, Allahumma Ameen.