“For there are certain men crept in unawares, who were before of old ordained to this condemnation.” (Jude 1:4)
Jude speaks severely of these “certain men” who were “before ordained” (literally “written about beforehand”) for a very specific judgment. The context relates back to the period of the Old Testament, although Jude later identifies others who are apparently active in the early churches.
A purification of 30 days was required of “certain men” who were (apparently) undertakers during the time of Moses. They were “defiled” by their contact with dead bodies according to the law but must still keep the Passover—albeit a month after the other Israelites (Numbers 9:4-11). God does not allow excuses.
Later, “certain men” among the Israelites who had apostatized and become “children of Belial” were to be destroyed, along with their city and all of their possessions, after it had been definitely determined that they had left Israel and become part of a cult community (Deuteronomy 13:13-16). God does not take prisoners!
During the time of Jeremiah’s ministry, God allowed the evil king Jehoiakim to send “certain men” down into Egypt to capture the prophet Urijah so the king could kill him (Jeremiah 26:22-23). God does allow evil men to gain the upper hand temporarily as He brings about the fulfillment of His prophetic warnings—in this case, the captivity of Judah by Babylon.
Jude speaks of “certain men” who had been “written before” (prographo) as historical examples of those among the New Testament saints who were “denying the only Lord God, and our Lord Jesus Christ” (v. 4b). Peter puts it this way: “But there were false prophets also among the people, even as there shall be false teachers among you, who privily shall bring in damnable heresies, even denying the Lord that bought them, and bring upon themselves swift destruction” (2 Peter 2:1). HMM III