Higher and nobler than all ordinary ones are another set of teachers, the Avataras of Ishvara, in the world. They can transmit spirituality with a touch, even with a mere wish. The lowest and most degraded characters become in one second saints at their command. They are Teachers of all teachers, the highest manifestations of God through man.
We cannot see God except through them. We cannot help worshipping them; and, indeed, they are the only ones whom we are bound to worship. …
No man can really see God except through these human manifestations. If we try to see God otherwise, we make for ourselves a hideous caricature of Him, and believe the caricature to be no worse than the original.
There is a story of an ignorant man who was asked to make an image of the God Shiva, and who, after days of hard struggle, manufactured only the image of a monkey. So, whenever we try to think of God as He is in His absolute perfection, we invariably meet with the most miserable failure; because as long as we are men, we cannot conceive God as anything higher than man. The time will come when we shall transcend our human nature, and know Him as He is; but as long as we are men, we must worship Him in man and as man. Talk as you may, try as you may, you cannot think of God except as a man.
Source - The Complete Works of Swami Vivekananda, 9 vols (Calcutta: Advaita Ashrama, 1–8, 1989; 9, 1997), 3.53–4.