Apostasy in Christendom refers to religious rebellion. It is the withdrawal of loyalty or a breaking away from the leadership or authority of God. An apostate is a practicing Christian that once pledged allegiance to God and the Bible doctrines, then afterwards turned back to live contrary to his avowed belief and declaration of faith. On the other hand, a reformer refers to a person that is making efforts to bring back those that strayed from godly commitments, to the proper form of Christian life. A reformer would do everything possible to instruct apostates, Christians and unbelievers, in the complete renewal of biblical structures of Christianity.
Apostasy occurred in several places in the Bible, and each occurrence reveals God's displeasure and terrible anger against apostates and anyone that incites the people to rebel against Him. I have frequently shared stories of several individuals who came to accept Jesus at the peak of their troubles when their situations were hopeless, and later decided to abandon God after they had received divine solutions to their problems through Jesus. Some years ago, when we tried to follow-up on one of such people, he said that a hospitalised fellow is usually allowed to go home after a successful medical treatment. He viewed the Church as a hospital and thought he didn't have any business with God whatsoever after being healed. The end of such ungrateful and rebellious people is always worse than their beginning. I pray that you will not be overcome by the spirit of apostasy in Jesus' name. Hebrews 6:4-6 says:
"For it is impossible for those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost, And have tasted the good word of God, and the powers of the world to come, if they shall fall away, to renew them again unto repentance; seeing they crucify to themselves the Son of God afresh, and put him to an open shame."

It is important to note that apostasy is not a casual sin but a voluntary rejection of God's will. It is a conscious departure from the Fatherhood of God, and a deliberate walk away from Jesus Christ and everything He stands for. This is the reason why the above Bible passage presents apostasy as a terrible error that is virtually impossible to remediate. May the Lord deliver anyone that is in any form of backsliding today in Jesus' name.
On the other hand, the main assignment of a reformer is to call the Church of God and His people into genuine repentance and a careful reconciliation between contemporary Christian practice and Bible doctrines. The body of Christ must be delivered from end-time lukewarmness, modernism, and the doctrine of relativity that is presently holding it in captivity. May we yield ourselves to be used as the Lord raises reformers that will re-ignite the fire of revival in the body of Christ today in Jesus' name. Written by Pastor E.A. Adeboye.