14 What would you then? That He who came for our salvation should become a minister of destruction because men could not bear Him? Or that He should suit His grace to our measure? Daniel could not bear the vision of an Angel, and were thou capable of the sight of the Lord of Angels? Gabriel appeared, and Daniel fell down: and of what nature or in what guise was he that appeared? His countenance was like lightning; not like the sun: and his eyes as lamps of fire, not as a furnace of fire: and the voice of his words as the voice of a multitude, not as the voice of twelve legions of angels; nevertheless the Prophet fell down.
And the Angel comes unto him, saying, Fear not, Daniel, stand upright: be of good courage, your words are heard. And Daniel says, I stood up trembling: and not even so did he make answer, until the likeness of a man's hand touched him. And when he that appeared was changed into the appearance of a man, then Daniel spoke: and what says he? O my Lord, at the vision of You my inward parts were turned within me, and no strength remains in me, neither is there breath left in me. If an Angel appearing took away the Prophet's voice and strength, would the appearance of God have allowed him to breathe?
And until there touched me as it were a vision of a man, says the Scripture, Daniel took not courage. So then after trial shown of our weakness, the Lord assumed that which man required: for since man required to hear from one of like countenance, the Saviour took on Him the nature of like affections, that men might be the more easily instructed.
Source: Catechetical Lectures (New Advent)