Shaikhul-Islaam said, “The one who abuses (the Messenger), if he is a Muslim – then he becomes a kaafir and is killed – about which there is no disagreement – and this is the position of the Four Imams and others – and as has preceded some such as Ishaaq ibn Rahawaih and others have declared that there is Ijma` about that.” [as-Saarimul-Maslool `alaa Shaatimin-Rasool]

He also said about one who abused the Messenger, sallallahu `alahhi wa sallam: “So anyone who abuses him or speaks ill of him – from those who declare him to be a Messenger – then that is a proof of his wicked belief and his kufr – indeed it is a proof of his taking him as a joke and a mockery, so if a proof has appeared about his inner state then no notice is taken of the outer appearance since we known that inwardly he is different.” [as-Saarimul-Maslool `alaa Shaatimin-Rasool]

Ash-Shaikh `Alee al-Malikee says: “So if anyone speaks against the pure Sharee`ah and the rulings which Allaah has laid down for his servants upon the tongue of His Messenger (sallallahu `alayhi wa sallam) then he is a definite kaafir – if he declares that openly he is an apostate (Murtad) and either he repents or he is killed, and if he seeks to hide that then he is a hypocritical heretic (Zindeeq) who is killed even if he repents. If however he speaks against a person and his state and his practicing the Deen – then he is abusing a Muslim – and its punishment is as the judge sees fit and whether this will be different to the first case will be determined by confession and examination of the circumstances, and some of them make the same as the first case with regard to its ruling. And as is known the Great Qur’aan is from the Deen and abusing it is kufr.” [Fathul-`Alee al-Maalik fil fataawaa `alaa Madhhabil Imaam Malik” (2/347)

And the committee of scholars of Saudi Arabia answered the question: ‘What is the ruling for the one who abuses the Deen if he is ignorant – does he have the excuse of ignorance or not in this case?’

The reply was: “Abusing Allaah or His words or anything from Him is kufr – and likewise abusing the Messenger, sallallahu `alayhi wa sallam, or his Sunnah or anything from it, or abusing the Deen of a person – if his Deen is Islaam – so if he is ignorant of that then the ruling must be explained to him – and if he does not give up his abusing then he is a kaafir and an apostate, outside Islaam – he either repents or is executed as Allaah says: ‘Say: Was it Allaah, and His Ayaat and His Messenger that you were mocking?’ Make no excuse; you have disbelieved after you had believed.’ [9:65-66] (Fatwaa no. 5213, dated 15/1/1403H.)