John Calvin Commentary Isaiah 13:15

"Every one that is found shall be thrust through; and every one that is taken shall fall by the sword." — Isaiah 13:15 (ASV)

Every one that is found shall be thrust through. Here he confirms what he had previously said: that no one will escape from Babylon, and that all who will be there will perish.

Xenophon also relates that, by Cyrus's command, they killed everyone they met at the beginning of the night; and the next day, they killed all who had not laid down their arms.

But we have already said that the prediction extends further. That slaughter was only the forerunner of others, for which Babylon was intentionally preserved, so that it might be frequently ruined.

And every one that is joined to them shall fall by the sword. Some translators render this clause differently than I have. Because the Hebrew verb ספה (saphah) signifies to destroy or consume, they read it, Whosoever shall be destroyed.

They explain this as relating to the old men, who were already worn out with age and could not live much longer anyway; as if he had said, “Not even the men of advanced age, who are sinking into the grave, will be spared, even though they are half-dead and appear to be already giving up the ghost.”

But because that is a weak interpretation, and the verb ספה (saphah) also signifies to add, I rather agree with Jonathan and others, who think that it denotes companies of soldiers; just as in taking a city, soldiers are gathered together in the form of a wedge to ward off enemy attacks.

However, perhaps it will be considered better to understand it as the confederates or allies who were joined to Babylon, and who could be said to be united in the same body, to show more fully the shocking nature of this calamity.