Philo Judaeus De Plantatione 64

[64] For, in real truth, the mind which is perfectly purified, and which knows all the things of creation, knows and recognizes one only God, the Uncreate, whom it approaches, and by whom it is received. For to whom is it permitted to say, "He alone is my God," except to the man who is attached to none of the objects which are inferior to him? And this is the custom of the Levites; for the name of Levi, being interpreted, means, "he is to me," because different things are honoured by different people, but by him only that which is highest and most excellent, the Cause of all things.