It goes without saying that da`wah (inviting others to Islam) is the best vocation and the noblest field for workers who want to gain the best in this world and in the afterlife. Almighty Allah says what means: “And who is better in speech than him who prayeth unto his Lord and doeth right, and saith: Lo! I am of those who surrender (unto Him).” (Fussilat: 33)
Sheikh `Abdul-Aziz bin Baz, the former Mufti of Saudi Arabia stated that: “Women, like men, are obliged to call people to Allah and to enjoin what is good and forbid what is evil because the texts of the Qur’an and Sunnah indicate that, and the words of the scholars clearly state that. So women have to call people to Allah and enjoin what is good and forbid what is evil, following the guidelines of Shari`ah, just as men are required to do. A woman should not be deterred from calling people to Allah by feelings of anxiety or lack of patience because of some people looking down on her, insulting her or mocking her. Rather she has to put up with that and be patient. If she thinks that people are mocking her or making fun of her in some way, then she should pay attention to something else, which is that she should be the best example of observing hijab in front of non-mahram men (those that are not forbidden in marriage) and avoid mixing freely.
She should be careful to ensure that her da`wah is free of anything reprehensible. If she makes da`wah to men she must do so while observing hijab and without being alone with any non-mahram man. If she makes da`wah to women, she must call them wisely and make sure that her attitude and behavior are above suspicion so that no one will criticize her or ask “why doesn’t she start with herself?” She has to keep away from clothing that will distract people, and avoid all kinds of fitnah (temptation) such as displaying her beauty or speaking in a soft, attractive manner, for which she may be criticized. She must take care to call people to Allah in a manner that will not harm her religious commitment or her reputation.”