those who deny the truth say why was the quran not sent down to him in a single revelation? we sent it in this manner so that we might strengthen your heart. we gave it to you in gradual revelation.
وقال الذين كفروا لولا نزل عليه القرآن جملة واحدة كذلك لنثبت به فؤادك ورتلناه ترتيلا