Allah Taãla states that one reason for this Ummah being titled as the best of Ummahs, is the practice of 'commanding good and preventing evil'.
Nabi (Sallallaahu Álayhi Wasallam) states, "Whosoever from among you witnesses evil, he should change it with his hands. And if he is unable to do so then he should change it with his tongue. And if he is unable to do so with his tongue, then he should at least consider it to be wrong. And this is the weakest stage of Imaan." (Mishkãt)
Hadhrat Nuúmaan bin Basheer (Radhiallaahu Ánhu) says that Rasulullah (Sallallaahu Álayhi Wasallam) gave an example of people sailing on a boat having an upper deck and a lower deck. The people from the lower deck require water and request water from the people of the upper deck. The people from the upper deck refuse water so the people from the lower deck decide to make a hole on the floor of the ship and get water from the sea. Rasulullah (Sallallaahu Álayhi Wasallam) said, "If the people from the upper deck don't stop the people at the bottom from making a hole, the ship will sink and all the people travelling will drown." (Mishkãt vol. 2 p. 436)
Similarly, if people do not prohibit evil and sin in the society, the entire society - innocent and evil - will equally suffer.
Hadhrat Abu Hurayra (Radhiallaahu Ánhu) states that Rasulullah (Sallallaahu Álayhi Wasallam) said, "Command good and prohibit evil or else Allah will send such a punishment that will destroy everyone." (Ibid)
The above quotations of the Qurãn and Ahaadith of Rasulullah (Sallallaahu Álayhi Wasallam) are clear that commanding good and prohibiting evil is an emphasised injunction of Allah and His Rasul. Every person must carry out this injunction. All the Prophets (Álayhimus salaam) followed the footsteps of their respective Prophets and after the demise of their Prophet, they carried out the same mission. The Sahaaba of Rasulullah (Radhiallaahu Ánhum) spent their entire lives in commanding good and prohibiting evil. Since there is no Prophet to come, every Ummati of Rasulullah (Sallallaahu Álayhi Wasallam) is the deputy of the Prophet and has to carry on the mission of the Prophet. The people of Tabligh Jamaat sacrifice their time, wealth and comforts to undergo difficulty and hardships to go in the path of Allah - to carry out this Sunnah of the Prophets - commanding good and prohibiting evil.
As far as the Tabligh Jamaat is concerned, it is our humble view that they are acting upon this injunction of Allah Taãla and are fulfilling this obligation of Shariáh. the Jamaat advocates strict adherence to the Sunnah and confines itself within the ambit of the Shariáh. The purpose of any individual taking part in the noble work of Tabligh is firstly to reform oneself and dutifully save mankind from the fire of hell. The overwhelming success of the Jamaat is mainly because of the manifestation of the six points which involves the purification of the Naffs and the entity of Tawheed.
The word 'Tashkeel' literally means 'to form'. In the terminology of Tabligh, it means to urge the people to give time, to come out in the path of Allah for self reformation and propagating good for a number of days 3, 7, 40, 4 months, 1 year, etc. The number of days is also not compulsory, it is only recommended just as it is recommended that a person studying first aid, for example, serves one month as practicals. While he will not be an expert in medicine, he will know the basic things to do during an emergency. Similarly, a person going out for 3 days, 40 days, 4 months, etc. does not become an expert on Shariáh, but he will learn the basic requirements of Shariáh. The more time he gives, the more he will learn and perfect himself. The time frame is not a criteria according to Shariáh.
and Allah Ta'ala Knows Best
Mufti Ebrahim Desai, www.ask-imam.com