Thank you for the question on assurance of salvation, “Why are so many people on Quora saying that you can lose your salvation when the Bible says otherwise?”
The reason why individuals say that one can lose one’s salvation is that there is a failure to distinguish between relationship and fellowship with God.
Relationship has to do with one’s birth into the family of God. As I read the Gospel of John, believers are born of God (John 1:12–13). Once a person places his/her faith in Jesus Christ as his/her personal Savior (John 3:16), one has passed from death to life. That person is born of God, independent of his good works (Eph. 2:4–10). God declares that has eternal life because s/he has been born again by the Spirit of God. The words, eternal life, can’t include loss of salvation otherwise one doesn’t have eternal life.
Fellowship has to do with one’s walk in the family of God. The child of God may walk with God or walk disobediently from God. In his disobedience, that person is still a child of God. The Parable of the Prodigal Son illustrates this fully. The wayward son is still the father’s son. Hebrew speaks of God disciplining his wayward children for our good (Hebrew 12). It’s my understanding in John 15 that Jesus is speaking about fruitfulness of his followers, not salvation. If they fail to abide in Jesus, then their usefulness on earth is ended. God can’t use him/her in advancing the Kingdom of God, not that they are expelled from the Kingdom of God. They have missed out on the opportunity of gaining rewards for faithful service to God (I Cor. 3).
The objection to assurance of salvation is what is called “Easy Believism.” It’s the idea of “getting one’s ticket punch” to get to heaven and then one can live on earth as one wants or it can’t be that simple. Accepting Jesus as Savior and refusing to acknowledge him as Christ or Lord is to fail to understand who He is. All authority in heaven and on earth has been given to Jesus. Every knee will bow in heaven and on earth.
Since that is true, how can a believer refuse to bow and surrender one’s life to Jesus. Since Jesus knows his sheep, that sheep will respond to the voice of the Good Shepherd. The sheep may wander away, but the Good Shepherd hears the faint cry of the wayward sheep and brings that sheep back into the fold.
Summary: One can be a wayward sheep, but one is still a sheep of Jesus.
-Kingston