[§ 611]. In most conditional expressions the subjunctive mood should follow the conjunction. All the following expressions are conditional.
1. Except I be by Silvia in the night,
There is no music in the nightingale.
Shakspeare.
2. Let us go and sacrifice to the Lord our God, lest he fall upon us with pestilence.—Old Testament.
3.—— Revenge back on itself recoils.
Let it. I reck not, so it light well aimed.
J. Milton.
4. If this be the case.
5. Although my house be not so with God.—Old Testament.
6. He shall not eat of the holy thing unless he wash his flesh with water.—Old Testament.
Expressions like except and unless are equally conditional with words like if and provided that, since they are equivalent to if—not.