Ezekiel 4:3
Moreover take thou unto thee an iron pan, and set it for a wall of iron between thee and the city: and set thy face against it, and it shall be besieged, and thou shalt lay siege against it. This shall be a sign to the house of Israel.
Cross-reference
In Ezekiel 4:7, the same siege symbol continues with uncovered arm and prophesying against Jerusalem. Direct continuation.
Ezekiel 12:11 has Ezekiel say 'I am your sign' — directly matching the sign-act purpose stated in Ezekiel 4:3.
Ezekiel 24:24-27 repeatedly calls Ezekiel a 'sign' and explains his prophetic role, reinforcing the sign concept in Ezekiel 4:3.
In Ezekiel 21:2, the command to set face toward Jerusalem repeats the same prophetic judgment sign.
In Ezekiel 13:17, the command 'set your face' targets false prophetesses, reusing the same phrase as against Jerusalem.
Isaiah 8:18 says Isaiah and his children are 'signs' from God — similar to Ezekiel being a sign to Israel in Ezekiel 4:3.
Isaiah 20:3 records Isaiah's naked walking as a 'sign' — another prophetic sign-act parallel to Ezekiel's symbolic siege.