John Calvin Commentary Isaiah 36:12

"But Rabshakeh said, Hath my master sent me to thy master, and to thee, to speak these words? [hath he] not [sent me] to the men that sit upon the wall, to eat their own dung, and to drink their own water with you?" — Isaiah 36:12 (ASV)

And Rabshakeh said. From this we see the fierceness and insolence of the enemy, and from this it is also evident that Hezekiah’s kingdom was on the brink of ruin. For here, Rabshakeh speaks like a conqueror, and does not address Hezekiah as a king, but as if he were his slave.

Therefore, when we see Rabshakeh swollen with so much pride, we should also remember that Hezekiah was entirely overwhelmed and destitute of all confidence, so that he was regarded as ruined. From this we also infer that Rabshakeh was not sent to offer any conditions of peace, but rather to obtain an unconditional surrender and to strike the people with alarm, for Sennacherib had sent him for this purpose with a powerful army.

From this, he also boasts that he has nothing to do with the king and that he is addressing the people for their own advantage. To terrify them still more, he mentions the distress and calamities into which they will throw themselves if they choose to obey Hezekiah. He warns that they will perish from hunger and be compelled to eat and drink what is revolting. Therefore, he argues, their wisest course will be to surrender promptly and provide for their safety.