the unbelievers say why was the whole quran not sent down all at once to him? it was sent thus that we may keep your heart resolute. so we enunciated it by steps and distinctly.
وقال الذين كفروا لولا نزل عليه القرآن جملة واحدة كذلك لنثبت به فؤادك ورتلناه ترتيلا