Shirk (associating others with Allah in His Divinity or worship) is the opposite of Tawhid (belief in the Oneness of Allah/monotheism). Shirk is of three kinds, but actually it is of two kinds: Major Shirk and Minor Shirk.
It involves the devotion of all or some acts of 'Ibadah (worship) to anyone or anything other than Allah. It also involves abstinence from performing some of the Ma'lum minaddin biddarurah (necessarily known religious principles) ordained by Allah, such as offering Salah (Prayer) and observing Sawm (Fast) in Ramadan, or denial of some matters prohibited by Allah, which fall under the Ma'lum minad din biddarurah, such as Zina (premarital sexual intercourse and/or adultery), drinking Khamr (intoxicant) and the like. It may involve obedience to a human in violating the Commands of the Creator and deeming this violation as Halal (lawful), or obeying any man or woman, whether a president, a minister, a scientist or others, in opposing the Religion of Allah (Glorified and Exalted be He). Certainly, everything that involves devoting any part of worship to anyone other than Allah, such as supplicating to Awliya' (pious people), seeking their assistance or making vows to them, or involves deeming lawful what Allah has prohibited or annulling what Allah has ordained such as believing that Salah, Sawm, Hajj in spite of capability to perform it, or Zakah (obligatory charity) are not obligatory or absolutely impermissible, all this constitutes Major Kufr (disbelief) and Major Shirk, because this is a sort of contradicting Allah and His Messenger (peace be upon him).
Consequently, whoever deems lawful what Allah has prohibited from the Ma'lum minaddin biddarurah such as Zina, Khamr and undutifulness to parents or believes in the permissibility of banditry, sodomy, Riba (usury/interest) or the like of the acts that are wellknown to be prohibited by authority of the Nas (Islamic text from the Qur'an or the Sunnah) and Ijma' (consensus of scholars) is unanimously a Kafir (disbeliever)
may Allah safeguard us and will come under the same ruling as those who commit acts of Major Shirk.
The same ruling applies to anyone who mocks and ridicules religion, they will be guilty of major Kufr (disbelief), as Allah (Glorified and Exalted be He) says: Say: "Was it at Allâh (ﻋﺰ ﻭﺟﻞ), and His Ayât (proofs, evidence, verses, lessons, signs, revelations) and His Messenger (ﺻﻠﻰ ﺍﷲ ﻋﻠﻴﻪ ﻭﺳﻠﻢ) that you were mocking?" Make no excuse; you disbelieved after you had believed.
The same applies to making little of any matter glorified by Allah out of contempt and disdain, such as irreverence to the Mushaf (Qur'anbook), urinating over it, stepping on it, sitting on it or the like; the doer of this is a Kafir (disbeliever) by Ijma', because by doing so they belittle and disdain Allah Himself (Glorified be He). The Qur'an is the Word of Allah (Exalted be He). Anyone who belittles the Qur'an is belittling Allah (Glorified and Exalted be He). Scholars have explained such issues under the chapter of "The Ruling on the Murtad (apostate from Islam)".
In each of the Four Madhhabs (Hanafy, Maliky, Shafi'y, and Hanbaly) they conducted a chapter called "Chapter of the Ruling on the Murtad", in which they explained all types of Kufr (disbelief) and Dalal (deviation from what is right).
It is actually a noteworthy chapter, especially in this time where many types of Riddah (apostasy) have spread out and many people are confused about such matters. Therefore, if someone pays due attention to this chapter, they will know the nullifiers of Islam, acts leading to Riddah and types of Kufr and Dalal.
The other type: Minor Shirk
are the acts established by the Islamic texts of Qur'an and Sunnah as falling under the term "Shirk", but still they do not tantamount to major Shirk. They are called minor Shirk, such as Riya' (doing good deeds for show) and seeking reputation, as when reciting the Qur'an, offering Salah or calling to the Path of Allah and the like for the sake of showing off.
It is authentically reported that the Prophet (peace be upon him) said, "The thing that I fear most for you is minor Shirk." They said, "O Messenger of Allah! What is minor Shirk?" He said, "Riya'. Truly, Allah (may He be Blessed and Exalted) shall say on the Day the servants shall be recompensed for their deeds, 'Go to those for whom you were showing off with your deeds in worldly life and see if you can find with them recompense.'" (Related by Imam Ahmad with authentic Isnad [chain of narrators]on the authority of Mahmud ibn Labid AlAshhaly AlAnsary [may Allah be pleased with him])It was also narrated by AlTabarany, AlBaihaqy and some other narrators as Hadith Mursal (a Hadith with no Companion of the Prophet in the chain of narration) on the authority of Mahmud, who was previously mentioned. This narrator, Mahmud, was a young Sahaby (Companion of the Prophet) who did not hear any Hadith from the Prophet (peace be upon him). But the Hadith Mursal narrated by the Sahabah (Companions of the Prophet) are Sahih (authentic) and used as evidence by the scholars and some scholars reported this as a consensus.
An example for that kind of Shirk is when a Servant (of Allah) says, "What Allah wills and soandso wills", "Were it not for Allah and soandso", or "This is from Allah and soandso". All this is considered minor Shirk according to the Hadithnarrated by Abu Dawud, with an authentic Isnad, from Hudhayfah (may Allah be pleased with him) that the Prophet (peace be upon him) said, "Do not say, 'What Allah wills and soandso wills,' but say, 'What Allah wills, then afterwards what soandso wills.'"
This includes also the Hadithnarrated by AlNasa'y from Qutailah that "A Jew came to the Prophet (peace be upon him) and said, ' You commit Shirk, as you say, ' What Allah wills and what you will.' You also say, 'By the Ka'bah (when you swear).' Therefore, the Prophet (peace be upon him) ordered them, whenever they needed to swear, to say, 'By the Lord of the Ka'bah' and to say, ' What Allah wills, then afterwards what you will.'" According toanother report by AlNasa'y on the authority of Ibn