Subjunctive mood uses in dependent or subordinate clauses with "an."
Greek, Subjunctive Mood 2, use of subjunctive, "an", temporal, conditional, relative, locative, future more vivid, present general
Bible Study; Lecture; Sermon Prep
Future Seminarians; Ministers
Voelz, James, "Chapter 29.B.2" (2011). Elementary Greek. 118.