2 Thessalonians 2:3,4 says:
Let no man deceive you by any means: for that day shall not come, except there come the falling away first, and that man of sin be revealed, the son of perdition; who opposes and exalts himself above all that is called God, or that is worshiped; so that he as God sits in the temple of God, showing himself that he is God.
What is “the falling away”? Apostasy literally means “a leaving from a previous standing”. This phrase comes from the Greek word ἀποστασία (Strong’s 646e) transliterated as apostasia. It means “a revolt or defection”. Apostasia is from aphístēmi (Strong’s 868), which means “to leave or depart”. It is derived from apó (Strong’s 575) which means “away from” and histémi (Strong’s 2476) which means “stand”. So, the word apostasy refers to “a departure or desertion”. Christian apostasy is when a person or group departs from Biblical Christianity (sound doctrine) and adds or takes away from the Bible with their own man-made traditions opposing the Word, doctrines originating from demons or rules that oppose/contradict the Bible’s teaching.
Traditions of Man (Church/Pastor’s Traditions) vs. The Word of God (The Bible)
Jesus opposed the Pharisees because they put their own, man-made traditions over the Words of Christ and thus nullified Jesus Christ’s teachings. Jesus said to them:
Making the word of God of no effect through your tradition, which you have delivered: and many such things do you. (Mark 7:13)
The Pharisees were in trouble by Jesus because they “made the word of God of no effect through their own tradition”. This means they annulled, or canceled, the Word of God and its authority in their lives and even taught others to do the same. This comes from the Greek transliteration, akuroo (Strong’s 208), which means “to revoke or invalidate”. The origin of this word is from alpha (as a negative prefix) and kuros which literally means “authority”. In a nutshell, the pharisees would not put themselves under the authority of the Word of God (today this is the Bible) and thus nullified or canceled it by their own man-made traditions. People (and even professing Christians) do this today when they read other modern books while exalting modern authors’ teachings over Christ’s teachings. People do this today when they obey their pastors or churches at the expense of obedience to God’s Word, the Bible and putting it into practice. People who love the Word are not Pharisees.
Doctrines of Demons (Unsound doctrine/teachings that are disguised as good, but are not from God at all) vs. Sound Doctrine (The Bible)
The Bible teaches that this will happen in the last days, “Now the Spirit speaks expressly, that in the latter times some shall depart from the faith, giving heed to deceitful spirits, and doctrines of demons” (1 Timothy 4:1). We must test every teacher, teaching and practice to see if it is from God (1 John 4:1).
Good Doctrinal Fruit (Matthew 12:35; Matthew 7) vs. Bad Doctrinal Fruit (“Leaven” – Matthew 16:12; Galatians 5:9)
Often, when people speak of “fruit”, they forget that truth/good doctrine is a fruit. Anything that opposes “sound doctrine” is a lie, and thus, bad fruit. Ephesians 5:9 says that the fruit of the light is in all goodness, righteousness and truth. Christians must carefully examine “doctrinal fruit” in addition to the other fruits in Galatians 5:22. Persecution and suffering is not bad fruit (John 16:33; 2 Tim. 3:12; Phil. 3:10).