London — Ayatollah Ruhollah Khomeini, the Iranian leader, ordered the Islamic courts to crack down decisively on counterrevolutionaries. The order came indirectly in a message to armed forces Chief of Staff Valiollah Fallahi broadcast by Tehran Radio. The ayatollah also hinted at a new armed forces purge, saying: "At the same time as people are obliged to identify plotters and plotting groups and hand them over to the judicial authorities, it is incumbent on the armed forces . . . to bring forward to the commanders those who are misguided or misled among them so they can be purged and punished."