Like to these is the saying of God to Moses: “Lo, I have set you in a cleft of the rock, and you shall see my back parts.” That rock which is Christ is therefore not completely closed but has clefts. But the cleft of the rock is he who reveals God to men and makes him known to them; for “no one knows the Father, save the Son.” So no one sees the back parts of God–that is to say, the things that are come to pass in the latter time–unless he be placed in the cleft of the rock, that is to say, when he is taught them by Christ’s own revealing.

–Origen, Commentary on the Song of Songs 3.15.