Psalms 81:5

5 He set it for a testimony in Joseph. The Hebrew word עדוה, eduth, is by some derived from עדה, adah, which signifies to adorn; and they translate it the honor or ornament of Joseph. But it rather comes from the verb עוד, ud, to testify; and the scope of the passage requires that it should be translated a testimony or covenant. Farther, when Joseph is named in particular, there is a reference to the first original of the chosen people, when, after the death of Jacob, the twelve tribes were distinguished. As the sovereignty had not at that time come to the tribe of Judah, and as Reuben had fallen from his right of primogeniture, the posterity of Joseph justly had the pre-eminence, on account of the benefits which he had been instrumental in conferring; having been the father and nourisher of his brethren and of the whole nation. Moreover, the sacredness of the covenant is commended by a special appeal to the fact, that at the time when God stipulated that this honor should be yielded to him, he had purchased that people to himself; as if it had been said, The condition upon which the people were delivered was, that they should assemble together on the days appointed for renewing the remembrance of the grace which had been exercised towards them. The words when he went forth will apply equally to God and to the people. It is a common form of expression to speak of God as going forth before his people, as a shepherd goes before his flock, or as a general before his army. When it is said ABOVE the land of Egypt, some think there is an allusion to the situation of Judea, which was higher than that of Egypt; so that those who come out of Egypt to Judea ascend. But I understand the language as meaning simply, that the people, having God for their conductor, passed freely and without obstruction through the land of Egypt, the inhabitants having been so discouraged and dismayed as not to dare to make any opposition to their passage. The prophet enhances the blessing of their deliverance, when, speaking in the name of the whole people, he affirms that he had been rescued from profound barbarism: I heard a language which I understood not. Nothing is more disagreeable than to sojourn among a people with whom we can hold no communication by language, which is the chief bond of society. Language being, as it were, the image and mirror of the mind, those who cannot employ it in their mutual intercourse are no less strangers to one another than the wild beasts of the forest. When the Prophet Isaiah (Isaiah 33:19) intends to denounce a very dreadful punishment, he says, “Thou shalt see a fierce people, a people of a deeper speech than thou canst perceive; of a stammering tongue, that thou canst not understand.” Thus the people acknowledge that the benefit which God conferred was so much the more to be valued, because they were delivered from the Egyptians, with whose language they were unacquainted.