Thomas Aquinas Commentary Jeremiah 31:18-19

"I have surely heard Ephraim bemoaning himself [thus], Thou hast chastised me, and I was chastised, as a calf unaccustomed [to the yoke]: turn thou me, and I shall be turned; for thou art Jehovah my God. Surely after that I was turned, I repented; and after that I was instructed, I smote upon my thigh: I was ashamed, yea, even confounded, because I did bear the reproach of my youth." — Jeremiah 31:18-19 (ASV)

1. Here is given the acceptance of those who repent, to whom is promised an acknowledgment of their confession: I have surely heard, that is, I have heard them mercifully. I have surely seen the suffering of my people, who are in Egypt, and I have heard their cry (Exodus 3:7). And the confession is given: you have chastised me, O Lord, and I was chastened, as a calf, who is corrected with difficulty and with many blows. Only vexation gives understanding to hearing (Isaiah 28:19).

2. Second, the petition is given: turn me and I shall be turned. Turn us, O Lord, to yourself, and we shall be turned; renew our days as from the beginning (Lamentations 5:21).

3. Third, the reason for the petition is given as arising from the repentance which he has begun.As noted above, in the Hebrew, the subject of this passage is more clearly Ephraim, who, by synecdoche, stands for the nation of Israel, whom Jeremiah will also call, virgin Israel (Jeremiah 31:21), below.

   1. First is the punishment: after you turned me, by infusing grace, I struck my thigh. This signifies interior grief by an exterior blow, in the manner of a grieving person. Or, I struck my thigh, by repressing carnal pleasures. With the hearing of the ear I have heard you, but now my eye sees you (Job 42:5).

   2. Second is repentance. Because from the punishment he has endured, recognizing his sin, he has suffered shame, which was a sign of repentance: I was put to shame, inwardly; I blushed, outwardly, for I have borne the reproach—that is, punishment and shame for the sins of my youth. He calls the time before his conversion “youth,” as if to say that he sinned out of ignorance. You write bitter things against me, and wish to destroy me with the sins of my youth (Job 13:26).