Ezekiel 9:7

‘And he said to them, “Defile the house and fill the courts with the slain. Go forth.” And they went forth and smote in the city.'

The house was to be deliberately defiled (compare Numbers 19:11; 1 Kings 13:2; 2 Kings 23:16). It was no longer God's temple. They had handed it over to idolatry, so that just as bones were scattered around the high places (Ezekiel 6:5), they would be around the temple precincts. It was a house of idolatry. And once that was so defiled then the visitants were to go out and destroy the city.