Charles Ellicott Commentary Isaiah 51:1

"Hearken to me, ye that follow after righteousness, ye that seek Jehovah: look unto the rock whence ye were hewn, and to the hold of the pit whence ye were digged." — Isaiah 51:1 (ASV)

Look unto the rock. —The implied argument is that the wonder involved in Israel's origin is a ground of faith in its restoration and perpetuity. The rock is, of course, Abraham; the pit, Sarah.