Then thou shalt see. — A various reading adopted by many commentators gives thou shalt Jear.
Thine heart shall fear... — Literally, shall throb, as with an awe-stricken joy at the marvellous prosperity, but that throb of awe is followed by the expansion of ecstatic joy.
The abundance of the sea — i.e., the riches of the Western isles, with which the new Jerusalem was to be filled, as Tyre and Zidon had been of old. (Ezekiel 27:1-25).