3 Would you learn that to comprehend the nature of God is impossible? The Three Children in the furnace of fire, as they hymn the praises of God, say Blessed are you that beholdest the depths, and sittest upon the Cherubim. Tell me what is the nature of the Cherubim, and then look upon Him who sits upon them. And yet Ezekiel the Prophet even made a description of them, as far as was possible, saying that every one has four faces, one of a man, another of a lion, another of an eagle, and another of a calf; and that each one had six wings, and they had eyes on all sides; and that under each one was a wheel of four sides. Nevertheless though the Prophet makes the explanation, we cannot yet understand it even as we read. But if we cannot understand the throne, which he has described, how shall we be able to comprehend Him who sits thereon, the Invisible and Ineffable God? To scrutinise then the nature of God is impossible: but it is in our power to send up praises of His glory for His works that are seen.
Source: Catechetical Lectures (New Advent)