Hilary of Poitiers — as excerpted in the Catena Aurea on John 6:22-27

“(viii. de Trin. c. 44) A seal throws out a perfect impression of the stamp, at the same time that it takes in that impression. This is not a perfect illustration of the Divine nativity: for sealing supposes matter, different kinds of matter, the impression of harder upon softer. Yet He who was God Only-Begotten, and the Son of man only by the Sacrament of our salvation, makes use of it to express the Father’s fulness as stamped upon Himself. He wishes to shew the Jews He has the power of giving the eternal meat, because He contained in Himself the fulness of God.”