Those Who Mock The Religion

Question :

Please clarify the meaning of this verse:
"If you ask them (about this), they declare: "We were only talking idly and joking." Say: "Was it at Allah, and His verses, and His Messenger that you were mocking?"

Answer:

This verse, or more correctly, a set of verses including this one were revealed about a group of hypocrites, who during a journey, were speaking idly to pass the time on the long trip and to forget its hardships. So they were- and we seek refuge in Allah Almighty - saying, "We have not seen people who desire food more, whose tongues are more prone to lying, and who are more cowardly upon meeting the enemy than our reciters." They were referring to the Companions of Allah's Messenger These hypocrites were lying, for they had the largest stomachs and a greater desire for food than others. They were the worst liars, and they were the most cowardly on the battlefield. What could show their cowardice more than the battle of Uhud, when they abandoned the battlefield, showing both their cowardice and their lack of faith.

So when these hypocrites said those words, Allah Almighty revealed these verses about them. They went to the Messenger of Allah ﷺ, and when he asked them what they said, they replied, "We were merely talking idly and jokingly we were speaking as travellers do, trying to while away the hours of our journey." Allâh Almighty said :
"Say: Was it at Allah and His verses and His Messenger that you were mocking? Make no excuse, you have disbelieved after you had believed.

From this verse we learn that mocking Allah Almighty, His signs, or His Messenger is disbelief it takes one outside of the fold of Islam, for Allâh Almighty said:
"You have disbelieved after you had believed."

Question :

And does this verse apply to those who mock people for growing their beards, for reducing the length of their garments, or in general, for following the Prophet's Sunnah?

Answer:

Those who mock people that adhere to Allâh's religion and Allah's orders, if they are mocking them because of this that they practice, then their mockery is a mockery of the Shari'ah. And mocking the Shari'ah is disbelief.

But if they are mocking them not because they follow the Sunnah regarding clothes, or growing the beard, but for some other reason, something that has nothing to do with them following the religion, then they are not committing an act of disbelief. If they are mocking them because of these practices of theirs, and directly mention such practices while mocking them, then this is disbelief, because they are mocking Allâh's Shari'ah.

But if he is mocking the person himself, not mentioning anything about Allâh's religion, then this is not disbelief. But it is obligatory for everyone to beware of mocking the people of knowledge or religious people who are known for applying the precepts of the religion and for following Allah's Book and the Sunnah of His Prophet ﷺ.

Source:
Ibn 'Uthaimin
Fatawa Islamiyah, Vol. 7 Pages 137-138-139