Charles Ellicott Commentary Jeremiah 3:7

"And I said after she had done all these things, She will return unto me; but she returned not: and her treacherous sister Judah saw it." — Jeremiah 3:7 (ASV)

And I said ... —The call to Israel to return had been slighted, and Judah, the traitress or faithless, “one with falsehood,” had not taken warning from the sin or its punishment.

Turn thou unto me.— The verb may be either the second or third person, I said, you will return; or, I said, she will return, as expressing a hope rather than a direct return. The latter seems, on the whole, the preferable rendering.