Should the Basmallah be said after reciting Surah Faatiha? Should it be said out aloud if leading the prayer?
A scholar of the past has said:
… Nevertheless the correct view is that it is not to be recited out loud, although it is prescribed to recite it out loud if that serves a definite interest. Hence it is prescribed for the imam to do that – sometimes – for example, to teach the people who are praying behind him. It is permissible for the worshippers to recite a few words out loud sometimes, and it is also permissible for a man to forego something that is preferable, in order to soften hearts and unite people, lest they be put off from what is in their best interests. For example, the Prophet (blessings and peace of Allah be upon him) decided not to rebuild the Ka‘bah on the foundations of Ibraaheem, because Quraysh had only recently left Jaahiliyyah behind (and were new in Islam), and he was worried that they may be put off by that. He thought that the issue of uniting people and softening their hearts took precedence over the issue of rebuilding the Ka‘bah on the foundations of Ibraaheem. Ibn Mas‘ood said, when he offered the prayer in full behind ‘Uthmaan, although he disliked that and objected to him about it, and he was questioned about that: “Dissent is evil.” Hence the imams or leading scholars, such as Ahmad and others, stated that the same applies in the case of the basmalah, and praying Witr as three continuous rak‘ahs, and other issues in which one may turn from that which is preferable to that which is permissible in the interests of softening the hearts or the obligation of teaching them the Sunnah, and so on.
End quote from Majmoo‘ al-Fataawa (22/436, 437).
He (may Allah have mercy on) also said: One may refrain from doing that which is preferable in one’s own opinion, lest the people be put off. The same applies if a man thinks that the basmalah should be recited out loud, but he is leading some people in prayer who do not think that that is recommended, or vice versa; if he goes along with them, that is fine.
End quote from Majmoo‘ al-Fataawa (22/268, 269).