BT San 18a(40) :היכא דאית ליה תקנתא בחזרה ניגלי דלית ליה תקנתא בחזרה לא ליגלי‏ : where he has the remedy of returning, he should go into exile (to the city of refuge. Where) he does not have the remedy (of returning) [e.g. a high priest who accidentally killed someone], he should not go into exile
See the entire entry for gly vb. to uncover; D to exile