O ye who believe! Let not some men among you laugh at others: It may be that the (latter) are better than the (former): Nor let some women laugh at others: It may be that the (latter are better than the (former): Nor defame nor be sarcastic to each other, nor call each other by (offensive) nicknames: Ill-seeming is a name connoting wickedness, (to be used of one) after he has believed: And those who do not desist are (indeed) doing wrong.
In verses 49:10-12, Allah has prescribed a number of things related to the preservation of brotherhood and what this implies with regard to what is to be held sacred among human beings. The first among these is the prohibition of mocking, deriding, and scoffing at others. The Believer who fears Allah and hopes to attain the Garden in the Hereafter will not scoff at any individual nor make people the object of his jokes, scorn, sarcasm or mockery, because this is nothing but pride, arrogance, and contempt for others, as well as ignorance of the scale by which Allah measures goodness. Says Allah Subhanahu wa Ta’ala: Let not some people mock at other people, for they may be better than themselves, nor (let) women (mock) at women who may better than themselves. (49:11)
In the scale of Allah, goodness is measured by faith, sincerity, and the quality of the relationship with Allah Ta’ala, not by physical appearance, wealth, or power. Said the Prophet (peace be on him). Allah does not look at your physical features or your wealth, but He looks at your hearts and your deeds. (Reported by Muslim.)
How, then, can it be permissible for a person to laugh at someone’s physical handicap, deformity, or poverty? It is reported that ‘Abdullah bin Mas’ood had thin, weak legs. Once, upon seeing his leg uncovered, some people laughed, whereupon the Prophet (peace be on him) said, Are you laughing at the frailty of his legs? By Him in Whose hand is my soul, in the scale of Allah they are weightier than Mount Uhud. (Reported by al-Tiyalisi and Ahmad.)
The Qur’an speaks of how the criminal idolaters used to laugh at the faithful Muslims, especially at the weak and oppressed ones like Bilal and ‘Ammar, and how the tables will be turned on the Day of Reckoning, when the mockers will become the mocked: Verily, the criminals used to laugh at those who believed and wink at one another when they passed them, and when they returned to their families they would return joking (about them). And when they saw them they would say, ‘Surely these people are astray.’ But they had not been sent as watchers over them. Then on this day those who believe will laugh at the disbelievers. (83:29-34)
Although it has already been implied in the first part of the verse 49:11, nevertheless this ayah goes on to state explicitly that women should not mock at other women. This emphasis is due to the fact that mocking at others is quite common among women.
The second of these prohibitions is against lamz, which literally means “piercing and stabbing.” Here it is used to mean finding faults, as the person who finds faults in others is doing something similar to piercing them with a sword or stabbing them with a dagger—and perhaps the wound inflicted by the tongue is more lasting. A poet has said,
The wounds of blades may heal one day,
But the wounds of the tongue? They never may.
The form of prohibition expressed in this verse is very subtle, saying, “Do not slander yourselves,” that is, one another. For the Qur’an regards the community of Muslims as one body in its mutual concerns and responsibilities, so that whoever slanders his brother in effect slanders himself.
One form of slandering is calling others by derogatory nicknames of the sort which highlight some defect and are used to mock and deride a person. A Muslim should not call his brother by a name which is offensive to him, thereby causing him pain and thus trampling on the feelings of Islamic brotherliness.
Al-Qaradawi, Yusuf (1960). The Lawful and Prohibited in Islam. http://www.islamicweblibrary.com/wp-content/uploads/2019/06/TheLawfulAndTheProhibitedInIslamal-halalWalHaramFilIslamByShaykhYusufAlQardawi.pdf