I will therefore put you in remembrance - That is, how such persons were proscribed, and condemned to bear the punishment due to such crimes.

Though ye once knew this - The word ἁπαξ, here translated once, has greatly puzzled many interpreters. It has two meanings in the sacred writings, and indeed in the Greek writers also.

1. It signifies once, one time, as opposed to twice, or several times.

2. Altogether, entirely, perfectly, interpreted by Suidas αντι τον διολου, ὁλοσχερως· and of this meaning he produces a proof from Josephus; This appears to be the sense of the word in Hebrews 6:4 : τους ἁπαξ φωτισθεντας· those who were Fully enlightened. Hebrews 10:2 : ἁπαξ κεκαθαρμενους· Thoroughly cleansed. See also Hebrews 10:3. Psalm 62:11 : ἁπαξ ελαλησεν ὁ Θεος. God spoke Fully, completely, on the subject. St. Jude is to be understood as saying, I will therefore put you in remembrance, though ye are Thoroughly instructed in this.

Saved the people - Delivered them from the Egyptian bondage.

Afterward destroyed them - Because they neither believed his word, nor were obedient to his commands. This is the first example of what was mentioned Jde 1:4.

put.

Romans 15:15 Nevertheless, brothers, I have written the more boldly to you in some sort, as putting you in mind...

2 Peter 1:12,13 Why I will not be negligent to put you always in remembrance of these things, though you know them...

2 Peter 3:1 This second letter, beloved, I now write to you; in both which I stir up your pure minds by way of remembrance:

having. See on

1 Corinthians 10:1-12 Moreover, brothers, I would not that you should be ignorant, how that all our fathers were under the cloud...

afterward.

Numbers 14:22-37 Because all those men which have seen my glory, and my miracles, which I did in Egypt and in the wilderness...

Numbers 26:64,65 But among these there was not a man of them whom Moses and Aaron the priest numbered...

Deuteronomy 2:15,16 For indeed the hand of the LORD was against them, to destroy them from among the host, until they were consumed...

Psalm 106:26 Therefore he lifted up his hand against them, to overthrow them in the wilderness:

Hebrews 3:16-19 For some, when they had heard, did provoke: however, not all that came out of Egypt by Moses...

Hebrews 4:1,2 Let us therefore fear, lest, a promise being left us of entering into his rest, any of you should seem to come short of it...

The Twofold Bearing of this Fact.
We come now to a point concerning which it behooves believers, particularly young believers and beginners in the study of prophecy, to be quite clear upon. Like the other two great Facts which we have reviewed--the First Advent of our Lord to this earth and His going away, and the presence now of the Holy Spirit upon this earth--this third great fact of the Redeemer's Return also has a double bearing, a bearing upon the Church and a bearing upon the world. The Second Coming of Christ will occur in …
Arthur W. Pink—The Redeemer's Return