Say, `I advise you (to do) one thing, (it is) that you keep Allâh (before) you, stand up in twos (- collectively) and ones (- singly) and then ponder (over the teachings of this Prophet). (You will come to the conclusion) that there is no vestige of insanity in (this) companion of yours (- Muhammad). He is only a Warner to you of a great calamity which is impending (over you).