Post by SHAYKH UMAR PAIKO

 "فإن  صلى خلف من يظن أنه مسلم ثم علم أنه كافر، أو أنه عابث، أو أنه لم يبلغ؛فصلاته تامة لأنه لم يكلفه الله تعالى معرفة ما في قلوب الناس. وقد قال عليه السلام:

"لم أبعث لأشق عن قلوب الناس وإنما كلفنا ظاهر أمرهم."

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"وأما من تأول في بعض ما يوجب الوضوء فلم ير الوضوء منه:فالإ ءتمام به جاءز"~الإمام ابن حزم في المحلى، كتاب الصلوة، المسألة  ٤١٢.

"And if one performs salaat behind someone he thought was a Muslim but later realised he(the Imaam) was a Kaafir or that he is playful in his Salaat or that the Imaam is a minor, his Salaat is complete because Allaah Has not compelled him to search out  people's thought.

And He (sallAllaahu alaihi wa aalihee wa sallam):

"لم أبعث لأشق على قلوب الناس، وإنما كلفنا ظاهر أمرهم."

"I have not been sent to pry into people's thoughts, we have only been compelled to judge them using their outward appearance."

But as for one who interprets an act  that vitiates ablution and opines that it doesn't nullify it, it is permissible to pray behind him."

~Ibnu Hazmin in Almuhallaa, article412."

It is known that the staunch Maalikiyyah scholars do not say BISMILLAAH before reciting faatihah in salaat. Ordinarily, salaat is null and void without faatihah and faatihah includes BISMILLAAH. However, we pray behind them because they misinterpreted some ahaadeeth in which the companions will say: he (sallAllaahu alaihi wa aalihee wa sallam) wasn't heard reciting BISMILLAAH before faatihah in salaat. The ahaadeeth were talking about reciting it aloud but many Maalikiyya generalise the exclusion whether in the salawaat in which recitation is aloud or otherwise. 

The fact that they rely on their (mis)interpretation of an authentic hadeeth is one reason why we pray behind them.

It is important to reflect on this!

سبحانك اللهم وبحمدك أشهد أن لاإله إلا أنت أستغفرك وأتوب إليك.