And it shall be, when they say unto thee, Wherefore sighest thou? that thou shalt answer, For the tidings; because it cometh: and every heart shall melt, and all hands shall be feeble, and every spirit shall faint, and all knees shall be weak as water: behold, it cometh, and shall be brought to pass, saith the Lord GOD. Wherefore sighest thou? - The prophet was a sign unto them.
His sighing and mourning showed them how they should act.
All knees shall be weak as water - See the note on Ezekiel 7:17.