This he ordained in Joseph for a testimony, when he went out through the land of Egypt: where I heard a language that I understood not.
All Commentaries on Psalms 81:5 Go To Psalms 81
Augustine of Hippo
8. "A testimony in Joseph He made that" (ver. 5). Look you, brethren, what is it? Joseph is interpreted augmentation. Ye remember, ye know of Joseph sold into Egypt: Joseph sold into Egypt is Christ passing over to the Gentiles. There Joseph after tribulations was exalted, and here Christ, after the suffering of the Martyrs, was glorified. Thenceforth to Joseph the Gentiles rather belong, and thenceforth augmentation; because, "Many are the children of her that was desolate, rather than of her that hath the husband." "He made it, till he should go out of the land of Egypt." Observe that also here the "fifth of the sabbath" is signified: when Joseph went out from the land of Egypt, that is, the people multiplied through Joseph, he was caused to pass through the Red Sea. Therefore then also the waters brought forth creeping things of living souls. No other thing was it that there in figure the passage of that people through the sea foreshowed, than the passing of the Faithful through Baptism; the apostle is witness: for "I would not have you ignorant, brethren," he said, "that our fathers were all under the cloud, and all passed through the sea, and were all baptized unto Moses in the cloud and in the sea." Nothing else then the passing through the sea did signify, but the Sacrament of the baptized; nothing else the pursuing Egyptians, but the multitude of past sins. Ye see most evident mysteries. The Egyptians press, they urge; so then sins follow close, but no farther than to the water. Why then dost thou fear, who hast not yet come, to come to the Baptism of Christ, to pass through the Red Sea? What is "Red"? Consecrated with the Blood of the Lord. Why fearest thou to come? The consciousness, perhaps, of some huge offences goads and tortures in thee thy mind, and says to thee that it is so great a thing thou hast committed, that thou mayest despair to have it remitted thee. Fear lest there remain anything of thy sins, if there lived any one of the Egyptians!
But when thou shalt have passed the Red Sea, when thou shalt have been led forth out of thine offences "with a mighty hand and with a strong arm," thou wilt perceive mysteries that thou knowest not: since Joseph himself too, "when he came out of the land of Egypt, heard a language which he knew not." Thou shalt hear a language which thou knowest not: which they that know now hear and recognise, bearing witness and knowing. Thou shalt hear where thou oughtest to have thy heart: which just now when I said many understood and answered by acclamation, the rest stood mute, because they have not heard the language which they knew not. Let them hasten, then, let them pass over, let them learn.