And God said unto Abraham,—probably in a dream, or night vision (vide Genesis 21:14)—Let it not be grievous in thy sight because of the lad, and because of thy bondwoman;—who was never recognized by God as Abraham's wife (cf.
Genesis 16:8)—in all that Sarah hath said unto thee, hearken unto her voice. Though Sarah's counsel was approved by God, it does not follow that her conduct was. On a former occasion Abraham's hearkening unto Sarah's voice had led to sin (Genesis 16:2); this time it would lie exactly in the line of duty.
For in Isaac shall thy seed be called. Literally, in Isaac shall seed (i.e. posterity) be called to thee; meaning neither, "by Isaac shall thy seed be called, or named" (Hofmann, Kalisch, Ainsworth), nor, "in Isaac shall thy seed be called into existence" (Dreschler); but, "in Isaac shall there be posterity to thee which shall pass as such," i.
e. be called or recognized as such (Keil); or, more simply, "in Isaac," i.e. in the line of Isaac, "shall be called to thee a seed," i.e. a seed par excellence, the seed already promised (Bleek, Delitzsch, Rosenmüller, Alford, Murphy).