Ezekiel 4:1-3

“You also, son of man, take a clay tablet and lay it before you, and portray on it a city, Jerusalem. Lay siege against it, build a siege wall against it, and heap up a mound against it; set camps against it also, and place battering rams against it all around. Moreover take for yourself an iron plate, and set it as an iron wall between you and the city. Set your face against it, and it shall be besieged, and you shall lay siege against it. This will be a sign to the house of Israel.