John Gill 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)

But Rabshakeh said, has my master sent me to your master, and
to you, to speak these words ?
&c.] That is, to them only, that he should use a language only understood by them: has he not sent me to the men that sit upon the wall ;
and therefore it is proper to speak in a language which they understand.

And to let them know that if they will not surrender up the city, but will attempt to hold out a siege, they must expect that they may eat their own dung, and drink their own piss with you ?
suggesting that they must expect a close siege, which would not be broke up until the city was taken; the consequence of which would be such a famine, that they would be reduced to such extremities.

The Jews have substituted other words in the margin, instead of those in the text, as more cleanly, and less offensive; for "dung" they put "excrement", and for "piss" they read "the waters of the feet"; and had we in our version put excrement and urine instead of these words, it would have been more decent.