" What awe must have come to the hearts of that waiting band as they listened to that “sound as of the rushing of a mighty wind”—what a sense of the irresistible power of God! But there was also the appearance of “tongues parting asunder, like as of fire.” Fire typifies the activity of God’s holiness in relation to sin; fire consumes and fire purifies. When the Spirit came upon Christ, it was not as the fire but “as a dove,” for there was no sin in Him, as the Father then declared, “Thou art my beloved Son; in thee I am well pleased” (Luke 3:22). But here the tongues “like as of fire” sat upon each of them, bringing not only a sense of the infinite holiness of God but of the activity of that holiness in dealing with all that was unholy in themselves. "

― Arthur Wallis , In the Day of Thy Power: The Scriptural Principles of Revival