Question: When people come to the Gathering Place (Mahshar) on the Day of Judgment, will all people, the good and the evil, be mixed? Or will the good people be kept separate from the others?
ANSWER
The Qur'an al-karim says (what means): "You all will come in groups" (An-Naba' 18).

The meaning of this Qur'anic verse was asked to our master the Prophet, and he explained it at length. It was stated that people would come to the Gathering Place in various forms according to their deeds. The following is said at the end of the hadith-i sharif:
(The ones who will be in the shape of monkeys will be those who carry one's talk to the other. The ones who will be in the shape of pigs will be eaters of haram. The ones who will move on their heads will be eaters of interest. The ones who will be blind will be those who do injustice when passing judgment. The ones who will be dumb and deaf will be those who have a high opinion of their deeds. The ones whose tongues will hang down to their chests will be scholars who do not practice what they preach. The ones whose hands and feet will be cut off will be those who harass their neighbors. The ones who will come spreading obnoxious smell will be those who drink, who commit fornication, and who do not pay the zakat. The ones who will be wearing garments made of tar will be those who are arrogant and conceited toward people. May Allahu ta'ala protect from them all.) [Tibyan]

It is also reported that there will be people who will come to the Gathering Place by assuming different forms in addition to the mentioned ones. However, it should be noted that the points explained above concern people who commit sins and have died without making repentance for them. Those who have made repentance or those whose rewards are more than their sins will not be brought to the Gathering Place in such forms.

Therefore, a wise person should never take a sin lightly and should abstain from all sins.