O YOU who have attained to faith! No men shall deride [other] men: it may well be that those [whom they deride] are better than themselves; and no women [shall deride other] women: it may well be that those [whom they deride] are better than them­selves. And neither shall you defame one another, nor insult one another by [opprobrious] epithets: evil is all imputation of iniquity after [one has attained to] faith;  and they who [become guilty thereof and] do not repent - it is they, they who are evildoers!

The Prophet said, "A Muslim is the one who avoids harming Muslims with his tongue and hands. And a Muhajir (emigrant) is the one who gives up (abandons) all what Allah has forbidden."