Allah said,

﴿وَلْتَكُن مِّنْكُمْ أُمَّةٌ﴾

(Let there arise out of you a group of people)

that calls to righteousness, enjoins all that is good and forbids evil in the manner Allah commanded,

﴿وَأُوْلَـئِكَ هُمُ الْمُفْلِحُونَ﴾

(And it is they who are the successful.)

Ad-Dahhak said, "They are a special group of the Companions and a special group of those after them, that is those who perform Jihad and the scholars.''

The objective of this Ayah is that there should be a segment of this Muslim Ummah fulfilling this task, even though it is also an obligation on every member of this Ummah, each according to his ability. Muslim recorded that Abu Hurayrah said that the Messenger of Allah said,

«مَنْ رَأَى مِنْكُمْ مُنْكَرًا فَلْيُغَيِّرْهُ بِيَدِهِ، فَإِنْ لَمْ يَسْتَطِعْ فَبِلِسَانِهِ، فَإِنْ لَمْ يَسْتَطِع فَبِقَلْبِهِ، وَذلِكَ أَضْعَفُ الْإِيمَان»

(Whoever among you witnesses an evil, let him change it with his hand. If he is unable, then let him change it with his tongue. If he is unable, then let him change it with his heart, and this is the weakest faith.) In another narration, The Prophet said,

«وَلَيْسَ وَرَاءَ ذَلِكَ مِنَ الْإِيمَانِ حَبَّةُ خَرْدَل»

(There is no faith beyond that, not even the weight of a mustard seed.)

Imam Ahmad recorded that Hudhayfah bin Al-Yaman said that the Prophet said,

«وَالَّذِي نَفْسِي بِيَدِه، لَتَأْمُرُنَّ بِالْمَعْرُوفِ، وَلَتَنْهَوُنَّ عَنِ الْمُنْكَرِ، أَوْ لَيُوشِكَنَّ اللهُ أَنْ يَبْعَثَ عَلَيْكُمْ عِقَابًا مِنْ عِنْدِهِ، ثُمَّ لتَدْعُنَّــهُ فَلَا يَسْتَجِيبَ لَكُم»

(By He in Whose Hand is my soul! You will enjoin righteousness and forbid evil, or Allah shall send down a punishment from Him to you. Then, you will supplicate to Him, but He will not accept your supplication.)

At-Tirmidhi also collected this Hadith and said, "Hasan''. There are many other Hadiths and Ayat on this subject, which will be explained later.