We recently heard this mentioned, and we believe it was in a teaching by Rico, but cannot locate it. He said (if it was Rico)that it was Yeshua that walked between the pieces, making covenant with Abraham. So even though God has issued a certificate of divorce to Ephraim, meaning they could not become His bride again, until Yeshua died on the execution stake, freeing them from the adulatry they had entered into.
This may seem hazy, as we are not clear on it, and want to check the scriptures further on this.