Charles Ellicott Commentary Jeremiah 31:2

"Thus saith Jehovah, The people that were left of the sword found favor in the wilderness; even Israel, when I went to cause him to rest." — Jeremiah 31:2 (ASV)

The people which were left of the sword ... —The main thought of this and the next verse is that the past experience of God’s love is a pledge or earnest for the future. Israel of old had found grace in the wilderness . But as the prophet has in his thoughts a new manifestation of that love, his language is modified accordingly. He thinks of the captives who had escaped, or would later escape, the sword of the Chaldeans (there had been no such deliverance in the case of the Egyptian exodus), and of their finding grace in the wilderness that lies between Palestine and the Euphrates. The verses that follow show, however, that the prophet is also thinking of the more distant exiles, the ten tribes in the cities of the Medes beyond the Tigris (2 Kings 17:6).

Even Israel, when I went to cause him to rest. —The verb that corresponds to the last five words includes the meaning of “settling” or “establishing,” as well as of giving rest; and the whole clause is better translated Let me go, or I will go (the verb is in the infinitive with the force of an imperative, but this is its meaning) to set him at rest, even Israel.