Jeremiah 31:15

"Thus saith Jehovah: A voice is heard in Ramah, lamentation, and bitter weeping, Rachel weeping for her children; she refuseth to be comforted for her children, because they are not. Thus saith Jehovah, Refrain thy voice from weeping, and thine eyes from tears; for thy work shall be rewarded, saith Jehovah; and they shall come again from the land of the enemy. And there is hope for thy latter end, saith Jehovah; and thy children shall come again to their own border. 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. Is Ephraim my dear son? is he a darling child? for as often as I speak against him, I do earnestly remember him still: therefore my heart yearneth for him; I will surely have mercy upon him, saith Jehovah."

The great emphasis in this paragraph is upon repentance and the tenderness and forgiveness by which true repentance shall be welcomed by the loving father.

This promise is not a picture of Ephraim's repentance, but a picture of the welcome that he would have received from God if he had repented. Over and beyond that, it emphasizes the necessity of repentance as a key element in the New Covenant to be announced a moment later. As Jesus expressed it twice in three lines, "Verily, verily, I say unto you, except ye repent, ye shall all likewise perish!" (Luke 13:3,5).

As far as the Northern Israel was concerned, there is no Biblical evidence whatever that any such wave of repentance as that suggested here ever happened.