Making fun of some aspects of the Sunnah
Question

                What is the ruling on making fun of the beard, short clothes and other aspects of the Sunnah? What is your opinion on those who, when these acts of worship are enjoined upon them, point to their hearts and say “Piety is here”?
Praise be to Allah.
    Making fun of the beard or clothes whose length etc. is in 
    accordance with the Sunnah or other aspects of the Sunnah makes a person a 
    kaafir, if he knows that this was proven from the Prophet  (peace and 
    blessings of Allaah be upon him), because he is thereby making fun of the 
    words and actions of the Prophet  (peace and blessings of Allaah be upon 
    him). In this case he is opposing the Prophet  (peace and blessings of 
    Allaah be upon him) and making fun of his Sunnah, and the one who makes fun 
    of the Sunnah and knowingly mocks things that are proven to be part of the 
    Sunnah is not a Muslim.

     Allaah says (interpretation of the meaning):

     “Say: ‘Was it at Allaah, and His Ayaat (proofs, evidences, 
    verses, lessons, signs, revelations, etc.) and His Messenger that you were 
    mocking?’

    Make no excuse; you disbelieved after you had believed”

    [al-Tawbah 9:65-66]

    If a person is called to observe one of the rulings of Islam 
    and says that piety is in the heart but he does not follow the shar’i 
    ruling, he is an evil liar. For faith includes both words and deeds, it is 
    not simply the matter of what is in the heart. This view is the same as that 
    of the evil innovators of the Murji’ah who restricted faith to the heart and 
    said that it had nothing to do with outward actions. Moreover, if the heart 
    is sound and filled with faith, that will be manifested in a person’s 
    actions. The Prophet  (peace and blessings of Allaah be upon him) said: 
    “In the body there is a piece of flesh which, if it is sound, the entire 
    body will be sound, and if it is corrupt, the entire body will be corrupt. 
    Indeed it is the heart.” (Narrated by al-Bukhaari, 52; Muslim, 1599). And he 
    also said: “Allaah does not look at the outward appearance or wealth of any 
    one of you; rather he looks at your hearts and deeds.” (Narrated by Muslim, 
    2564)

     Whatever the case, these words of those who stubbornly 
    refuse to follow the truth and carry out the commands of Islam is a sign of 
    their lack of faith by means of which they want to stop those who seek to 
    call them to Islam and advise them.