What is the ruling on those who say that shaving the beard and making one's garment shorter are trivial matters and are not basic principles of religion, or those who laugh at those who do these things?.
This suggestion is serious and is a grievous mistake. There are no trivial issues in Islam, rather all of it is serious and is aimed at guiding man to the best way. It is divided into basics and minor issues, and the issues of the beard and shortening the garment come under the minor issues, not basic issues. But it is not permissible to call any of the issues of religion insignificant. There is the fear that the person who says such a thing by way of belittling or mocking may be apostatizing from his religion thereby, because Allaah says (interpretation of the meaning):
“If you ask them (about this), they declare: ‘We were only talking idly and joking.’ 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”
The Messenger peace and blessings of Allaah be upon him) is the one who enjoined letting the beard grow and trimming the moustache; it is essential to obey him and to heed his commands and prohibitions in all matters.
Abu Muhammad ibn Hazm narrated that there was scholarly consensus that letting the beard grow and trimming the moustache is something obligatory, and undoubtedly happiness, salvation, pride, honour and good consequences lie in obeying Allaah and His Messenger, and doom, loss and bad consequences lie in disobeying Allaah and His Messenger. Similarly, wearing one’s clothes above the ankles is obligatory because of the words of the Prophet (peace and blessings of Allaah be upon him): “Whatever part of the lower garment hangs below the ankles is in the Fire.” (Narrated by al-Bukhari in his Saheeh). And he (peace and blessings of Allaah be upon him) said: “There are three to whom Allaah will not speak on the Day of Resurrection, nor even look at them or praise them, and theirs will be a painful torment: the one who lets his lower garment hang below his ankles; the one who reminds others of things he has given to them; and the one who sells his product by means of false oaths.” (Narrated by Muslim in his Saheeh). And he (peace and blessings of Allaah be upon him) said: “Allaah will not look at the one who lets his garment drag out of pride.” (Agree upon).
So the Muslim man must fear Allaah by shortening his garment above the ankles, whether it is a galabiyah, an izaar (lower garment, waist-wrapper), pants or abayah (cloak), and not letting it come down below his ankles. It is better if it comes to mid-calf length. If the isbaal (letting the garment hang below the ankles) is done because of pride or arrogance, the sin is more serious; if it is because of carelessness and not because of pride, it is still an evil action and the one who does it is a sinner according to the more correct of the two scholarly views, but his sin is less serious than the sin of one who does it out of pride. Undoubtedly isbaal is a means that leads to arrogance even if the one who does claims that he is not doing it out of pride, because the warning in the ahaadeeth is general, so it is not permissible to take this matter lightly.
With regard to the story of al-Siddeeq (Abu Bakr), when he said to the Prophet (peace and blessings of Allaah be upon him), “My izaar (lower garment) slips down unless I pay attention to it”, and the Prophet (peace and blessings of Allaah be upon him) said to him, “You are not one of those who do it out of arrogance,” this applies to those whose case is like that of Abu Bakr with regard to their garment slipping down by mistake, not because of arrogance, but they still try not to let that happen. As for those who let their garment drag deliberately, this warning applies to them but not to people like Abu Bakr.
As well as the warning mentioned above, isbaal (letting the garment hang below the ankle) is also a kind of extravagance and exposes the garment to dirt and impurities, and it is an imitation of women. All of that dictates that the Muslim should protect himself from that. And Allaah is the Source of strength and the Guide to the straight path.