The isles; i.e. the distant countries of the West (see on Jeremiah 2:10). So great an event as the restoration of the chosen people would be of worldwide importance. He that scattered Israel will gather him, etc.
"The Israelites were the flock of Jehovah (Psalms 77:20; Psalms 80:1), but during the Captivity a scattered and miserable flock. Jeremiah says that his eye 'shall run down with tears, because the flock of Jehovah is carried away captive' (Jeremiah 13:17).
The change in the fortunes of the Jews is compared by the prophets to a shepherd's seeking his lost sheep, and feeding them again in green pastures (Jeremiah 31:10; Jeremiah 1:19; Ezekiel 34:11-16). The reference is not so much to the homeward journey of the exiles as to the state of temporal and spiritual happiness in which they would find themselves on their return.
The same figures occur in a psalm, where a reference to the return from exile is excluded by the pre-exile date, ' … feed them also, and carry them forever' (Psalms 28:9)" (from the writer's note on Isaiah 40:11).