classical せよ (imperative of する)

The classical imperative form of する — せよ — surviving today in formal, written, military, legal, religious, and aphoristic contexts. Modern colloquial equivalent is しろ; polite is してください. せよ carries elevated, literary authority: 注意せよ ('take care!'), 実行せよ ('execute!'), 脱出せよ ('evacuate!').