لا سهو على الامام إذا حفظ عليه من خلفه ولا على من خلفه إذا حفظ عليهم الامام فان شكوا كلهم وجب عليهم الاعادة
There is no (obligation for) prostration of forgetfulness (sahw) upon the imam (of prayer) if those behind him have maintained the correctness of the prayer for him, and there is no (obligation for) sahw upon those behind him if the imam (of prayer) has maintained it for them. But if all of them are in doubt, then it is obligatory upon them to repeat the prayer.