Isaiah 10:23

When God made statements such as "You shall not murder; you shall not commit adultery; you shall not steal; you shall not bear false witness," he was teaching me to refrain from doing to others what I would be unwilling to do to myself. Therefore the precept offered in the Gospel belongs only to the one who first drew it up in ancient times, arranging it according to his own teaching in a formula that could easily be understood. This was predicted in another passage in which the Lord, that is, Christ, was "to make a concise word on the earth."

What wonder, most beloved brothers, if such [the Lord's Prayer] is the prayer that God has taught, who by his instruction has abbreviated our every prayer in a saving word? This had already been foretold by Isaiah the prophet, when filled with the Holy Spirit, he spoke of the majesty and loving kindness of God. He said, "He will finish the word and cut it short in righteousness, because the Lord will make a short word in all the world." For when the Word of God, our Lord Jesus Christ, came to all, and gathering together the learned and unlearned alike, he gave forth the precepts of salvation to every sex and age, he made a concise compendium of his precepts. [This was] so that the memory of the learners might not be burdened in heavenly discipline but might learn quickly what was necessary to a simple faith.

I find, indeed, that some eminent writers have published treatises on these matters piously and briefly written. Moreover, I know that the heretic Photinus has written on the same, with the object not of explaining the meaning of the text to his readers but of wresting things simply and truthfully said in support of his own dogma. Yet the Holy Spirit has taken care that in these words nothing should be set down which is ambiguous or obscure or inconsistent with other truths; for therein is that prophecy verified, "Finishing and cutting short the word in equity: because a short word will the Lord make upon the earth." It shall be our endeavor, then, first to restore and emphasize the words of the apostles in their native simplicity.

(Verse 20 onwards) And it shall come to pass in that day, that the remnant of Israel shall no more stay upon him that smote them, but shall stay upon the LORD, the Holy One of Israel, in truth. The remnant shall return, even the remnant of Jacob, unto the mighty God. For though thy people Israel be as the sand of the sea, yet a remnant of them shall return: the consumption decreed shall overflow with righteousness. For the Lord God of hosts will make a consummation and an abbreviation in the midst of all the land.

But somebody will perhaps think that we lack nothing for the knowledge of righteousness, since the Lord, when He summarily and briefly expounded His word on earth, informed us that the whole law and the prophets depend on two commandments; nor was He silent as to what these were, but declared them in the plainest words: "Thou shalt love," said He, "the Lord thy God, with all thy heart, and with all thy soul, and with all thy mind;" and "Thou shalt love thy neighbour as thyself." What is more surely true than that, if these be fulfilled, all righteousness is fulfilled?