Dear readers, allow me to go into a little bit of detail. It is mandatory for every Muslim to propagate religion but only after acquiring full knowledge of all branches of Religion; one should not begin to consider himself to be a religious scholar only after going through translations of the Holy Qur'aan or reading a few other books by themselves.
According to a hadees of the holy Prophet, a person undertaking a journey for preaching and serving religion honestly and sincerely only for seeking Allaah's happiness, will receive 49 crore (490 million) times greater reward than for each of his prayers (Namaaz). Preaching the Religion is undeniably auspicous. But it is also a very delicate matter. During the caliphate of Hazrat Saiyidinaa Umar Faarooq-e-Aazam (Allaah be pleased with him), only four to five senior respected companions of the holy Prophet were permitted to issue verdicts. Beside them no one else was permitted to do so.
It is a saying (ahadees) of the holy Prophet (Alaiehis Salaatu Was Salaam), "Anyone of you who sees anything happening against Sharee' at and Sunnat infront of their eyes, then the person seeing this should try to stop it within his powers; if he cannot afford to do this, he should raise his voice against it; and if even this is not possible for him, he should at least consider it wrong in his heart; but only considering it as evil within one's heart is the lowest degree of Ieemaan (faith)." (Muslim, Abu Da’ud, Nasai, Ibn-e-Majah, Masnad-e-Ahmad)
According to this statement of the holy Prophet (Sallal Laahu ‘Alaiehi Wa Sallam), it is mandatory on every Muslim to try to the best of their capacity to fight firmly against the opponents of Religion.
Excerpt - White & Black- Allamah Kaukab Noorani Okarvi