Allaah (The Most High) said:
وَمِمَّنۡ خَلَقۡنَآ أُمَّةٌ۬ يَہۡدُونَ بِٱلۡحَقِّ وَبِهِۦ يَعۡدِلُونَ
And of those whom We have created, there is a community who guides (others) with the truth, and establishes justice therewith.” [7:181]
That is: And of all those I (Allaah) created, there is a virtuous community, (who strive to) perfect themselves and others. They are guided and guiding others to the truth [i.e. foremost amongst them are the scholars of Tawheed and Sunnah (1)]. They know the truth and act upon it. They make it known, call to it and (encourage others to) act upon it.
[وَبِهِۦ يَعۡدِلُونَ -And establishes justice therewith] between the people in their judgements, when they judge in affairs of wealth, blood (i.e. crime of murder, injury, capital punishment etc.), the rights of the people and other than that. These ones are the leaders of guidance and the lamps that (banish) darkness.
They are the ones whom Allaah bestowed with Eemaan, righteous action, commanding and recommend one another to the truth (i.e. order one another to perform all kinds of good deeds which Allah has ordained, and abstain from all kinds of sins and evil deeds which Allah has forbidden), and recommend one another to patience (for the sufferings, harms, and injuries which one may encounter in Allaah’s Cause during preaching His religion of Islamic Monotheism etc).
They are the truthful ones, whose status comes after the status of Mesengership. They are of different levels amongst themselves-each of them in accordance with his state of (piety) and lofty status. Glorified and Exalted Be Allaah who bestows His special Mercy to whosoever He wills and Allaah is the Owner of great bounty.
[Source: Tayseer Al-Kareem Ar-Rahmaan Fee Tafseer Kalaam al-Mannaan’ by Imaam Sadi (rahimahullaah; slightly paraphrase and abridged]