John Calvin Reformed @genevareformer

Then when he says, that Zion was built by blood, and Jerusalem by iniquity, it is the same as though the Prophet had said, that whatever the great men expended on their palaces had been procured, and, as it were, scraped together from blood and plunder.

Matthew Henry Presbyterian @wholebiblehenry

Here, I. The prophet experiences a divine power going along with him in his work, and he makes a solemn profession and protestation of it, as that which would justify him, and bear him out, in his plain dealing with the princes and rulers.

Commenting on Micah 3:8-12

John Gill Reformed Baptist @doctorgill

They build up Zion with blood, and Jerusalem with iniquity. Or, "O thou that buildest up" (g), &c. or "everyone of them that buildeth up" (h), &c. for the word is in the singular number; but, be fire words rendered either of these ways, they respect the heads and princes of the people; who either repaired the temple on Zion, or ornamented the king's palace...