Isaiah 51:2

Look unto Abraham your father,.... Not only the father of the Jewish nation, but of all them that believe: this explains what is meant by the rock, in the former verse, who is to be looked unto for imitation in the exercise of faith, and performance of duty, and for encouragement in distressed times and circumstances:

and unto Sarah that bare you; signified by the pit or cistern; who was not only the mother of the Jewish nation; but such also are her daughters who do well, and tread in her steps: now the very unpromising circumstances these two persons were in, are proposed to be considered by the church in her present ones, for the encouragement of her faith; that as a numerous issue proceeded from them, so also should she become fruitful and multiply:

for I called him alone, and blessed him, and increased him; he was without issue when he was "called" out of Chaldea into another country, and also the only one of the family; and the Lord "blessed" him not only with flocks and herds, and gold and silver, but with a son in his old age; and so "increased" him, that there sprung from him as many as the stars of the sky in multitude, and as the sand by the sea shore innumerable, Hebrews 11:12. The Septuagint and Arabic versions, between "blessed" and "increased", insert these words, "and I loved him", which are not in the Hebrew text. The Targum is,

"and one was Abraham, alone in the world, and I brought him to my service, and I blessed him, and multiplied him.''