[20].Surah Taha [Tâ-Hâ]: Ayat 92-94

Ayat 92. [Mûsa (Moses)] said: "O Harun (Aaron)! What stopped you when you saw them going astray;

Ayat 93. "That you followed me not (according to my advice to you)? Have you then disobeyed my order?"

Ayat 94. He [Harun (Aaron)] said: "O son of my mother! Seize (me) not by my beard, nor by my head! Verily, I feared lest you should say: 'You have caused a division among the Children of Israel, and you have not respected my word!' "

[Tafseer] "From following me? Didst thou then disobey my order?"  Moses, when he came back, was full of anger and grief. His speech to Aaron is one of rebuke, and he was also inclined to handle him roughly: see next verse. The order he refers to is that stated in Surah Aaraf 7: Ayat 142. "Act for me amongst my people: do right, and follow not the way of those who do mischief." (Aaron) replied: "O son of my mother! Seize (me) not by my beard nor by (the hair of) my head! Truly I feared lest thou should say, ´Thou has caused a division among the children of Israel, and thou didst not respect my word!´" This reply of Aaron's is in no way inconsistent with the reply as noted in 7:150. On the contrary, there is a dramatic aptness in the different points emphasized on each occasion, and Aaron rightly says: "The people did indeed reckon me as naught, and went near to slay me!" In adding, "Let not the enemies rejoice over my misfortune" he is referring by implication to his brother's wish to maintain unity among the people. Here the unity is the chief point to emphasize: we are dealing with the Samiri as mischief-monger, and he could best be dealt with by Moses, who proceeds to do so.

Hazrat Saeed Al-Khudri (May Allah be pleased with him) reported: The Messenger of Allah [SAWW](PBUH) said, "Whoever amongst you sees an evil, he must change it with his hand; if he is unable to do so, then with his tongue; and if he is unable to do so, then with his heart; and that is the weakest form of Faith".

[Muslim Book 01,Chapter 21, Hadith # 80] 

Lesson : as mentioned above in Surah Taha Ayat 92."What stopped you when you saw them going astray" This Hadith contains a very important prescription to prevent the Muslim society from all things which are forbidden in Islam. So long as Muslims adhered to it and ceaselessly and fearlessly performed their obligation of enjoining the right and forbidding the wrong, their society was largely safe from many evils and sins.