As for their internal ruling, some of them are obligatory and some of them are Sunnah. As for rinsing the mouth, the obligatory part of it is to pronounce “There is no god but God,” for with it your tongue is purified from polytheism and your chest, for its letters are from the chest and the tongue. Likewise, in every obligatory prayer, God has made it obligatory for you to utter something that does not take your place in it. Other than you, it is waived from you as a sufficient obligation, like a blind man who sees at a distance who wants to fall into a pit and will be harmed by falling into it or perish. It is obligatory upon him to call out and warn him against falling, with what is understood to be about him, because he will not catch it. If a person precedes him to that, that obligation that he was obligated to do is waived from him, so if he speaks it. It is good for him and not obligatory for him, so if he rinses his mouth with this and others like it, then he has done good