Of the Man Who Brought Before Him His Son, Whom the Disciples Were Unable to Heal; And of the Question Concerning the Agreement Between These Three Evangelists Also in the Matter of the Order of Narration Here
116 Matthew goes on in the following terms: “And when He had come to the multitude, there came to Him a certain man, kneeling down before Him, and saying, Lord, have mercy on my son; for he is lunatic, and sore vexed;” and so on, down to the words, “Howbeit this kind is not cast out but by prayer and fasting.” Both Mark and Luke record this incident, and that, too, in the same order, without any suspicion of a want of harmony.
Source: The Harmony of the Gospels (New Advent)