The term "heresies" only appears three times in the Bible (1 Cor. 11:19, Gal. 5:20, and 1 Peter 2:1). "Heresy" is only used one time and can be found in Acts 24:14. Whenever these terms are used, they are always connected with a false teaching.
Unless a person is grounded in the Word of God, they will be easily swept away by false teachings. Similar to witchcraft, this work of the flesh has a dual application as it applies to both the teacher and the believer.
Let's take a look at what the Apostle Peter said about heresies:
"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." - 1 Peter 2:1
Notice that the person that brings in heresies is a teacher. Heresies cannot enter into a church unless they are taught to the members (cf. Revelation 2:14-15). It is the role of an elder to know and teach sound doctrine only (1 Tim. 5:17, Titus 1:9). Elders are also supposed to not be given over to greed (1 Peter 5:2).
The Catholic church is an example of heresy that we can see today. I won't focus on the greed aspect because you can simply look at any Catholic church or the Vatican to see the sheer wealth that they have obtained. I do want to focus on what is taught because it is imperative that people understand that salvation is ONLY by His grace and not by our works (1 Cor. 15:1-4, Eph. 2:8-9).
Here are some excerpts from the Catechism of the Catholic Church and can be found on the Vatican's website:
"Baptism is the first and chief sacrament of forgiveness of sins because it unites us with Christ, who died for our sins and rose for our justification, so that 'we too might walk in newness of life.'"
- CCC 977
“Baptism is necessary for salvation for those to whom the Gospel has been proclaimed and who have had the possibility of asking for this sacrament. The Church does not know of any means other than Baptism that assures entry into eternal beatitude..." - CCC 1257
"Justification has been merited for us by the Passion of Christ. It is granted us through Baptism. It conforms us to the righteousness of God, who justifies us. It has for its goal the glory of God and of Christ, and the gift of eternal life. It is the most excellent work of God's mercy," - CCC 2020
“Baptism, by imparting the life of Christ's grace, erases original sin." - CCC 405
“Justification is conferred in Baptism, the sacrament of faith. It conforms us to the righteousness of God, who makes us inwardly just by the power of his mercy.” - CCC 1992
“The grace of Christ is the gratuitous gift that God makes to us of his own life, infused by the Holy Spirit into our soul to heal it of sin and to sanctify it. It is the sanctifying or deifying grace received in Baptism.” - CCC 1999
”The specific precepts of the natural law, because their observance, demanded by the Creator, is necessary for salvation.” - CCC 2010
"The Second Vatican Council confirms: 'The bishops, successors of the apostles, receive from the Lord... the mission of teaching all peoples, and of preaching the Gospel to every creature, so that all men may attain salvation through faith, Baptism and the observance of the Commandments'"
- CCC 2068
Many of these false teachings are spread throughout other denominations as well.
It is our responsibility to study the Bible (2 Tim. 2:15) in order to not be led astray. The more time we spend in the Bible, the more we know the truth and it is the truth that makes us free (Jn. 8:32). Notice that Jesus said "makes" and not "sets" us free. If we do not spend time in the Word and only rely on others to teach us the Bible, we put ourselves back into bondage when Jesus said that we are free.
Paul said in Galatians to "stand fast therefore in the liberty wherewith Christ hath made us free, and be not entangled again with the yoke of bondage" (5:1). When we spend time in the Bible, we are not ignorant of Satan's devices (2 Cor. 2:11) and know what sound doctrine is (2 Tim. 3:16).
I do want to stress that there is a difference between committing heresy and speaking out of ignorance. Paul said that he "obtained mercy, because I did it ignorantly in unbelief" (1 Tim. 1:13). However, we are commanded not to remain ignorant (Rom. 1:13, 11:25; 1 Cor. 12:1; 1 Thess. 4:13). We are not supposed to remain as spiritual babies i.e. new Christians. We are supposed to mature.
Notice what Paul said to the Corinthian church and look at the list of sins in the works of the flesh: "And I, brethren, could not speak unto you as unto spiritual, but as unto carnal, even as unto babes in Christ. I have fed you with milk, and not with meat: for hitherto ye were not able to bear it, neither yet now are ye able. For ye are yet carnal: for whereas there is among you envying, and strife, and divisions, are ye not carnal, and walk as men? For while one saith, I am of Paul; and another, I am of Apollos; are ye not carnal?" - 1 Corinthians 3:1-4
Allowing ourselves to fall into heresy means that we are carnal Christians. We are supposed to be different from this world and not conformed to any false teachings (Rom. 12:2).
Next work of the flesh: envyings