Jude 1:14-16 meaning

This section draws on ancient Jewish traditions, specifically referencing a prophecy by Enoch, a figure known for his righteousness and closeness to God, who is said to be the seventh generation from Adam. Enoch was a righteous man that so pleased God that He took Him, apparently in a rapture event, since Enoch did "not see death" (Hebrews 11:5):

It was also about these men that Enoch, in the seventh generation from Adam, prophesied, saying, "Behold, the Lord came with many thousands of His holy ones, to execute judgment upon all, and to convict all the ungodly of all their ungodly deeds which they have done in an ungodly way, and of all the harsh things which ungodly sinners have spoken against Him" (vv 14-15). 

This part of Jude serves to underscore the impending judgment upon the ungodly and the prideful behaviors demonstrated by them. The quote from the non-biblical Book of Enoch in verse 14 comes from Enoch 1:9:

"And behold! He cometh with ten thousands of His holy ones to execute
judgement upon all,
And to destroy all the ungodly:
And to convict all flesh
Of all the works of their ungodliness which they have ungodly committed,
And of all the hard things which ungodly sinners have spoken against Him."
(Enoch 1:9) 

The first chapter of Enoch contains "The words of the blessing of Enoch." It begins with "The words of the blessing of Enoch, wherewith he blessed the elect and righteous, who will be living in the days of tribulation, when all the wicked and godless are to be removed" (Enoch 1:1). The chapter goes on to describe the time of God's judgement of the earth. In verse 7, Enoch says:

"And the earth shall be wholly rent in sunder
And all that is upon the earth shall perish,
And there shall be a judgement upon all."
(Enoch 1:7)

This is followed by the next verse, which says that "with the righteous He will make peace. And will protect the elect" (Enoch 1:8a). 

Then verse 9 expands on God's judgment of the ungodly. 

This follows a biblical consistency with respect to God's judgment; God judges all sin. When God judges the sin of His elect, they are refined (Psalm 66:10). When He judges His adversaries they are consumed (Hebrews 10:27). But in each case, unrighteousness is judged (Hebrews 10:31). 

The mentioning of Enoch's descent, in the seventh generation from Adam, highlights his prophetic authority, and the fact that this has been God's approach since the beginning of time. He promises in the past tense that the Lord came with many thousands of His holy ones. This is the prophetic past tense, which speaks of things which are to come as if they are already accomplished in order to emphasize the certainty of their fulfillment. 

Verse 15 unfolds the purpose of this divine arrival: to execute judgment upon all, and to convict all the ungodly of all their ungodly deeds which they have done in an ungodly way, and of all the harsh things which ungodly sinners have spoken against Him. The repetitive use of the term ungodly accentuates the gravity of the sins committed and amplifies the impending doom awaiting those who flaunt God's grace and continue in sin. 

God's judgment isn't merely about wrongful actions, but extends to the malicious words spoken against God, including all the harsh things which ungodly sinners have spoken against Him. Jesus asserts that we will give account in the day of judgment for every "careless word" that we speak (Matthew 12:35). How much more will anyone give account for speaking harsh things against God?

The next verse lists things that might be in view that constitute the harsh things spoken against God by the ungodly sinners:

These are grumblers, finding fault, following after their own lusts; they speak arrogantly, flattering people for the sake of gaining an advantage (v 16). 

The term grumblers brings to mind the Israelites who complained in the wilderness, at Massah, asking "Is the Lord among us, or not?" (Exodus 17:7). In saying this, the Israelites were essentially saying, "If God does not do our bidding, then He is not doing us any good, so we will find another god and choose a path independent of God" (Exodus 32:4; Numbers 14:4). 

Jesus quoted a verse from Deuteronomy that refers to this incident at Massah when resisting Satan's temptation to throw Himself down from the pinnacle of the temple to see if God would preserve Him:

"You shall not put the Lord your God to the test, as you tested Him at Massah." (Deuteronomy 6:16)

The faithful approach to God is to seek His ways, and trust they are for our best. The ungodly way of testing God is to insist that He perform for us, and give us what we demand. Then when God does not properly perform, the ungodly can be seen finding fault with Him, as Israel did in the wilderness. 

Just as Israel allowed their thirst to overwhelm their faith, the ungodly find themselves following after their own lusts. They trusted in their own desires rather than trusting in God. As a result of believing they knew better than God what was in their best interest—they speak arrogantly. Since they believe they know better than God, they elevate themselves above Him. Further, they manipulate others in order to exploit them, flattering people for the sake of gaining an advantage. 

Thus, rather than believing God's word that our own best interest is served by loving and serving others, these ungodly people follow their own lusts, and arrogantly pursue their own ways. They believe they know better than God. In their arrogance, they flatter and manipulate others to extract benefit from them, to serve their own appetites. Their interest in others is not genuine, but rather they seek to gain advantage to satisfy their own lust (James 1:14-15).