Jerome : And he promises to them, saying: This is my covenant with them, whether the agreement, as all others transferred, or the testament, as the Seventy have set forth. But what the covenant, agreement, and testament are, the following verse shows: My spirit, he says, who is in you, and my words that I have placed in your mouth, will not depart from your mouth, nor from the mouth of your seed, from now on and forever. What is said either to Isaiah, as it seems to me, or to the Lord, as most people think. Therefore, the order is connected to Isaiah in this way: This is the everlasting covenant of the Gospel, that my spirit which is in you, and my words which I have put in your mouth, by which you will foretell the future, may not depart from your mouth, nor from the mouths of your sons and grandsons, and your descendants, so that every generation may be shown: that is, that the grace of the Prophets may come in the Apostles, and through them, to those who will believe in Israel through the Apostles. But what He adds is in perfect harmony with this testimony: Heaven and earth shall pass away, but my words shall not pass away. — Commentary on Isaiah Theodoret of Cyrus : He calls "mouth" that of the apostles, and "seed" of the apostles those who learn from their teaching. Thus he promises grace of the Spirit to those who believe in him.… Thus, we who also enjoy this grace, let us sing praises to the fount of grace to whom glory is due for the ages of ages. Amen. — COMMENTARY ON Isaiah 18:59.21