Isaiah 51:1

Hearken to me, (a) ye that follow after righteousness, ye that seek the LORD: look to the (b) rock [from which] ye are hewn, and to the hole of the pit [from which] ye were dug.

(a) He comforts the Church, that they would not be discouraged for their small number.

(b) That is, to Abraham, of whom you were begotten, and to Sarah of whom we were born.