Ezekiel 21:7
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.
The sighing answers to tidings of God's coming judgment. That judgment was to come through Babylon's imminent attack upon Jerusalem. The news spread terror that melted every heart and made all hands feeble. Every spirit fainted and all knees grew weak as water under the report, leaving Judah's outlook hopeless.