The optative mood is generally used in the so-called
"fourth-class" conditions which express a wish or desire for
an action to occur in which the completion of such is
doubtful. By the time of the New Testament, the optative mood
was beginning to disappear from spoken and written Greek, and
such rarely occurs in the New Testament.
In a few cases, verbs in the optative mood stand apart from a
conditional clause to express the strongest possible wish
regarding an event. The most common of these appears in the
phrase "mh genoito" (AV, "God forbid"; NKJV "Certainly not").