Lift up your eyes, and behold them that come from the north: where is the flock that was given thee, thy beautiful flock?
Behold them that come from the north - Nebuchadnezzar and his hostile army (Jeremiah 1:14; Jeremiah 6:22).
Where is the flock that was given thee? Jeremiah, amazed at the depopulation caused by Nebuchadnezzar's forces, addresses Jerusalem (a noun of multitude, which accounts for the blending of plural and singular-Your eyes ... thee ... thy flock-and in the Hebrew "lift up-behold," is singular, "lift thou up, behold thou," and yet "your [instead of thins] eyes" follow, and asks where is her population (Jeremiah 13:17, "the Lord's flock") which God had given her?