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.
Zakah Al-Fitr is to be paid to those who are entitled to receive it based on the statement of Allaah Almighty (which means): {Zakah expenditures are only for the poor and for the needy and for those employed to collect [zakah] and for bringing hearts together [for Islam] and for freeing captives [or slaves] and for those in debt and for the cause of Allaah and for the [stranded] traveler—an obligation [imposed] by Allah. And Allaah is Knowing and Wise.} [Quran 9: 60]
Those who are most entitled to receive zakah are the poor and the needy, as indicated by a report that is attributed to Ibn ‘Abbas in which he said:
The Prophet, sallallaahu ‘alayhi wa sallam, enjoined zakah Al-Fitr as a means of purifying one’s fasting from indecent speech or behavior and as a means of helping the needy. Whoever pays zakah Al-Fitr before the Eid Prayer, it is accepted of him. As for whoever pays it after Eid Prayer, it is considered charity. [Abu Daawood, Ibn Majah, and Ad-Daaraqutni]
That being said, da‘wah activities are not one of the channels set by the sharia for zakah payment. It is incorrect to consider it part of the channel allocated to ‘the cause of Allah’ because, according to the correct opinion of the scholars, this category is concerned with jihad. To conclude, it is not permissible to pay zakah Al-Fitr for da‘wah activities.
Allaah Knows best.