therefore - Other oldest manuscripts and Vulgate read, “But”; in contrast to the ungodly Jud 1:4.
though ye once - rather, “once for all.” Translate, “I wish to remind you, as knowing ALL (namely, that I am referring to; so the oldest manuscripts, versions, and Fathers) once for all.” As already they know all the facts once for all, he needs only to “remind” them.
the Lord - The oldest manuscripts and versions read, “Jesus.” So “Christ” is said to have accompanied the Israelites in the wilderness; so perfectly is Jesus one with the God of the Israelite theocracy.
saved - brought safely, and into a state of safety and salvation.
afterward - Greek, “secondly”; in the next instance “destroyed them that believed not,” as contrasted with His in the first instance having saved them.