Duties of a Daa`iyah (caller to Islam)
7-3-2012 | IslamWeb
Question:
What are the duties of a caller to Allaah The Almighty?
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
It is the duty of whoever wants to work as a caller to the religion of Allaah The Almighty to combine both knowledge and practical application of this knowledge so that he becomes one of those who invite to Allaah The Almighty with insight. Allaah The Almighty Says (what means): {Say, "This is my way; I invite to Allaah with insight, I and those who follow me. And exalted is Allaah; and I am not of those who associate others with Him."}[Quran12:108]
Such a person also has to know the fixed foundations of Da‘wah (Islamic propagation) so that he does not deviate from them as a result of the hardships he faces in Da‘wah.
The questioner also has to realize that Da‘wah will not reap its fruit unless he is aware of people's circumstances. He has to become acquainted with what is going on in his society, since medicine is dispensed only after knowing the illness. Moreover, a preacher is not allowed to use prohibited means in his Da‘wah for it is not possible for a preacher to achieve the right through a wrong way, regardless of how decorated or adorned it might be. In past times, some people who were falsely called preachers used to tell lies about the Prophet, sallallaahu ‘alayhi wa sallam , and fabricate Hadeeths and ascribe them to him with the intention of urging people to observe worship. If anyone objected to that, they would reply that they only told lies for, and not against, the Prophet, sallallaahu ‘alayhi wa sallam.
Scholars never allowed such lies, even though they urge Muslims to act upon the Sunnah. Imaam As-Suyooti 
stated that there is consensus on that stance, and he also mentioned that Imaam Al-Juwayni firmly indicated that doing so intentionally would render a person a disbeliever.
Allaah Knows best.