This verse anticipates a time when the schism caused by Jeroboam is over. Ephraimite watchmen equally with the tribe of Judah watch for the new moon that they may go up to Jerusalem to keep the appointed Feasts.
Related Commentaries of Jeremiah 31:6
Jeremiah 31:6
6 For there shall be a day, that the watchmen upon the mount Ephraim shall cry, Arise ye, and let us go up to Zion unto the LORD our God.