Al-Hujurat 49:11

Ya ayyuha allatheena amanoola yaskhar qawmun min qawmin AAasa an yakoonookhayran minhum wala nisaon min nisa-in AAasaan yakunna khayran minhunna wala talmizoo anfusakum walatanabazoo bil-alqabi bi/sa al-ismualfusooqu baAAda al-eemani waman lam yatub faola-ikahumu aththalimoon

O you who have believed, let not a people ridicule [another] people; perhaps they may be better than them; nor let women ridicule [other] women; perhaps they may be better than them. And do not insult one another and do not call each other by [offensive] nicknames. Wretched is the name [i.e., mention] of disobedience after [one's] faith. And whoever does not repent - then it is those who are the wrongdoers.

O you who believe, no men should ever scoff at other men. May be, the latter are better than the former. Nor should women (ever scoff) at other women. May be, the latter women are better than the former ones. And do not find fault with one another, nor call one another with bad nicknames. Bad is the name of sinfulness after embracing Faith. If anyone does not repent, then such people are the wrongdoers.