Charles Spurgeon Commentary Romans 9:7

"neither, because they are Abraham`s seed, are they all children: but, In Isaac shall thy seed be called." — Romans 9:7 (ASV)

But, In Isaac shall thy seed be called.

By passing over Ishmael, God showed that there was no saving power in blood or birth. Ishmael was the firstborn son of Abraham; but he was passed by, for the promise was, In Isaac shall thy seed be called.