I think that the text is clear, the “they” in 2 Peter 2:20-22 does not refer to Christians who have lost their salvation, rather, the “they” refers to the false teachers that Peter has been describing in great detail from the start of chapter two. Peter writes to the Church, he writes to Christians, he would not use the pronoun “they” to refer to those [to] whom he writes. In verse 22 he quotes Proverbs 26:11, this passage clearly talks about the fool who rejects the wisdom of God, not one who did except (sic) that wisdom and then reject the wisdom of God.
This question most likely comes from one who accepts the doctrine of “once saved, always saved.” The question demonstrates the lengths to which people will go toe establish false doctrine. The Enquirer engages in all sorts of machinations to establish that the “they” in the passage have never been saved. Would it not be simpler to let the passage speak for itself? For if after they have escaped the pollutions of the world through the knowledge of the Lord and Saviour Jesus Christ, they are again entangled therein, and overcome, the latter end is worse with them than the beginning. 21 For it had been better for them not to have known the way of righteousness, than, after they have known it, to turn from the holy commandment delivered unto them. (Italics added for emphasis.) Peter clearly says of the “they” that they had escaped the pollutions of the world. This cannot be simply a compliment for committing less heinous sins, having escaped from such. The escape was obtained through the knowledge of the Lord and Savior Jesus Christ. To argue that “they” escaped the pollutions of the world but not the world is pure sophistry. Assuming arguendo that the “they” refers to false teachers, they were false teachers who at one time had “escaped the pollutions of the world” and later were “again entangled therein.” Peter even proclaims that “they” had known the way of righteousness and then turned away from it. Language could not be plainer. They were not “once saved, always saved.” Paul joins with Peter in acknowledging that Christians, even leaders in the church, can become false teachers. Acts 20:30. Proverbs 26:11, quoted by Peter, is not to the contrary. Throughout the history of the church some who have known the wisdom of God have turned away from the wisdom and made shipwreck of the faith. 1 Timothy 1:19-20.
Having said all of that, the scripture does speak of a way that the Christian can keep from falling or stumbling. “And beside this, giving all diligence,, add to your faith virtue; and to virtue knowledge; 6 And to knowledge temperance; and to temperance patience; and to patience godliness; 7 And to godliness brotherly kindness; and to brotherly kindness charity. 8 For if these things be in you, and abound, they make you that ye shall neither be barren nor unfruitful in the knowledge of our Lord Jesus Christ. 9 But he that lacketh these things is blind, and cannot see afar off, and hath forgotten that he was purged from his old sins. 10 Wherefore the rather, brethren, give diligence to make your calling and election sure: for if ye do these things, ye shall never fall. . . .” 2 Peter 1:5-10.
You Must Hear the Gospel
You must hear the gospel and then understand and recognize that you are lost without Jesus Christ no matter who you are and no matter what your background is. The Bible tells us that “all have sinned, and come short of the glory of God.” (Romans 3:23) Before you can be saved, you must understand that you are lost and that the only way to be saved is by obedience to the gospel of Jesus Christ. (2 Thessalonians 1:8) Jesus said, “I am the way, the truth, and the life: no man cometh unto the Father, but by me.” (John 14:6) “Neither is there salvation in any other: for there is none other name under heaven given among men, whereby we must be saved.” (Acts 4:12) "So then faith cometh by hearing, and hearing by the word of God." (Romans 10:17)
You Must Believe
You must believe and have faith in God because “without faith it is impossible to please him: for he that cometh to God must believe that he is, and that he is a rewarder of them that diligently seek him.” (Hebrews 11:6) But neither belief alone nor faith alone is sufficient to save. (James 2:19; James 2:24; Matthew 7:21)
You Must Repent
You must repent of your sins. (Acts 3:19) But repentance alone is not enough. The so-called “Sinner’s Prayer” that you hear so much about today from denominational preachers does not appear anywhere in the Bible. Indeed, nowhere in the Bible was anyone ever told to pray the “Sinner’s Prayer” to be saved. By contrast, there are numerous examples showing that prayer alone does not save. Saul, for example, prayed following his meeting with Jesus on the road to Damascus (Acts 9:11), but Saul was still in his sins when Ananias met him three days later (Acts 22:16). Cornelius prayed to God always, and yet there was something else he needed to do to be saved (Acts 10:2, 6, 33, 48). If prayer alone did not save Saul or Cornelius, prayer alone will not save you. You must obey the gospel. (2 Thess. 1:8)
You Must Confess
You must confess that Jesus Christ is the Son of God. (Romans 10:9-10) Note that you do NOT need to make Jesus “Lord of your life.” Why? Because Jesus is already Lord of your life whether or not you have obeyed his gospel. Indeed, we obey him, not to make him Lord, but because he already is Lord. (Acts 2:36) Also, no one in the Bible was ever told to just “accept Jesus as your personal savior.” We must confess that Jesus is the Son of God, but, as with faith and repentance, confession alone does not save. (Matthew 7:21)
You Must Be Baptized
Having believed, repented, and confessed that Jesus is the Son of God, you must be baptized for the remission of your sins. (Acts 2:38) It is at this point (and not before) that your sins are forgiven. (Acts 22:16) It is impossible to proclaim the gospel of Jesus Christ without teaching the absolute necessity of baptism for salvation. (Acts 8:35-36; Romans 6:3-4; 1 Peter 3:21) Anyone who responds to the question in Acts 2:37 with an answer that contradicts Acts 2:38 is NOT proclaiming the gospel of Jesus Christ!
You Must Be Faithful Unto Death
Once you are saved, God adds you to his church and writes your name in the Book of Life. (Acts 2:47; Philippians 4:3) To continue in God’s grace, you must continue to serve God faithfully until death. Unless they remain faithful, those who are in God’s grace will fall from grace, and those whose names are in the Book of Life will have their names blotted out of that book. (Revelation 2:10; Revelation 3:5; Galatians 5:4)