Apostasy (Kufur, or blasphemy), Riddah is to interrupt al-Islam.
Ridday is to say, do or believe in kufur which takes the Muslim out of Islam to kufur.
Riddah is divided into three categories. Such classification [was given] by an-Nawawiyy and other [^ulama’] from among the Shafi^iyyah, Hanafiyyah and other schools [of Islamic Law]. [It’s categories are]: Beliefs, doings and sayings.
The proof from al-hadith that it is not a condition for one to fall in al-kufr that the person knows the judgment.
The prophet, salla-l-lahu ^alayhi wa sallam, said: "A person may utter a word that he thinks harmless, but it results in his falling in Hellfire [the depth of ] 70 years [in travel]". That is, the distance covered in descending 70 years in Hellfire. This is the bottom of Hellfire (Jahannam) and it is only inhabited by the kuffar (non-Muslims, blasphemers). This hadith was narrated by at-Tirmidhiyy who classified it as hassan [i.e., authentic].
A hadith related by al-Bukhariyy and Muslim has a similar meaning. It says: The slave may utter a word that he thinks not haram, but it results in his falling in Hellfire [a deep distance] longer than that between the east and west. Al-hafidh Ibn Hajar said in Fath al-Bariyy when interpreting the aforementioned hadith: This includes what infers belittling Allah or His Islamic Laws. Those two hadith are a proof that it is not a condition for a person to commit kufr that he knows the judgment, feels delighted, or believes the meaning of the uttered [blasphemous] word. [Such a condition was] falsely stated as such in the book of <Fiqh as-Sunnah>. The book of <Fiqh as-Sunnah> has stipulated that this is a condition, but such a condition is unfounded.
The proof from al-Qur’an that belittling Allah or his messenger is kufr.
Allah ta^ala said:
The ayah means: If they [the kuffar] were questioned they would say we were just talking and joking. Say to them: Is it Allah, his ayat and messenger you were belittling!! Do not give any excuse. You committed kufr after you had the belief (at-Tawbah 65-66).
The name of one [Islamic reference] from those who conveyed the consensus about charging with kufr the person who cusses Allah Al-’imam al-qadi ^Iyad al-Yahsubiyy. In his book <ash-Shifa> he said: “There is no disagreement [among the Muslims] that a person from the Muslims who cusses Allah is kafir and deserves to be persecuted [by the Muslim ruler].”
The name of one [Islamic reference] from those who conveyed the consensus about charging with kufr the person who uttered a blasphemous word or did a blasphemous action. A: Taj ad-Din as-Subkiyy. He said in his book <Muqadimat at-Tabaqat>: “There is no disagreement among al-’Ash^ariyy and his companions, say rather among all the Muslims, that the person who utters a saying of kufr or does the doings of al-kuffar is a kafir about Allah al-^Adhim. Furthermore, he will dwell eternally in Hellfire, even though his heart knows [the truth]. However, knowledge does not benefit him with [his] stubbornness and does not protect him [from becoming kafir]. No two Muslims disagree about that [judgment].”
The judgment about the person who denies what is [apparently] known by necessity from the Religion
The person who denies something that is apparently known, which the ^ulama’ and common Muslim equally know, commits kufr. One is not excused unless he is a new Muslims or has been raised in a desert away from the ^ulama’ and does not know that this matter is from al-’Islam. Also, the matter in concern must not be related to clearing Allah of the partner and place [and the prophet from non-befitting attributes].
Al-^ulama’ classified the expressions into two categories: adh-dhahir and as-sarih. Adh-dhahir has according to language two meanings or more, but is more used in one of these meanings [than the others]. When a person utters an expression that is dhahir, he is not charged with kufr; unless, one knows about what the person meant by that saying. On the other hand, as-sarih does not have any other explanation. The one who utters a sarih statement which is kufr, commits kufr. He is not asked about what he meant and no explanation can be accepted from him; unless, he does not know the meaning of this sarih saying, because he may think that its meaning is other than what he said. In this case, this saying with regards to him does not carry the standing of as-sarih.
It is a must upon the one who committed ar-riddah to go back immediately to al-’Islam by uttering the two professions.
I bear witness that no one deserves to be worshiped except Allah and
I bear witness that Muhammad is the Messenger of Allah
In Arabic: أشهدُ أنْ لا إلهَ إلاَّ اللهُ وأشهدُ أنَّ محمّداً رسولُ الله
Transliteration: (Ashhadu Alla-Ilaha Illallah, Wa Ashhadu Anna Muhammadar-Rasulullah)
He has also to quit what caused ar-riddah, regret and determine not to commit it or its similar.