There are those who are proclaiming that the doctrine of eternal security is blasphemy are themselves speaking lies against the Holy Spirit. They are basically saying that the Holy Spirit jumps in and out of people based on their sin level.
When Christ changes us into a new creation it is a supernatural occurrence not of human effort.
1 Corinthians 3:15 " If any man's work shall be burned, he shall suffer loss: but he himself shall be saved; yet so as by fire."
Philippians 3:20-21 "20 For our citizenship is in heaven, from which also we eagerly wait for a Savior, the Lord Jesus Christ; 21 who will transform the body of our humble state into conformity with the body of His glory, by the exertion of the power that He has even to subject all things to Himself."
Ephesians 2:8-10 "…8 For it is by grace you have been saved through faith, and this not from yourselves; it is the gift of God, 9 not by works, so that no one can boast. 10 For we are God’s workmanship, created in Christ Jesus to do good works, which God prepared in advance as our way of life.…"
Anyone who believes they are keeping themselves saved through their own goodness is preaching a false gospel.
Ephesians 1:13-14
"13 In Him, you also, after listening to the message of truth, the gospel of your salvation—having also believed, you were sealed in Him with the Holy Spirit of the promise, 14 who is a first installment of our inheritance, in regard to the redemption of God’s own possession, to the praise of His glory."
We were sealed with the Holy Spirit of Promise when Christ changes us after we believed on Him. He changed us, He cleanses us for our lifetime and He takes us to our eternal home when we die.
1 John 2:19
"19 They went out from us, but they were not really of us; for if they had been of us, they would have remained with us; but they went out, so that [a]it would be evident that they all are not of us."
No one who has been changed by Christ ever turns from Him. If someone does they were never changed by Him. Those who turn back were like Judas, they knew of Christ and tasted of His goodness but never believed in Him and never confessed their sinfulness. These people never were given the Holy Spirit, they are false believers, pretenders among the flock.
Matthew 12:32
Whoever speaks a word against the Son of Man will be forgiven, but whoever speaks against the Holy Spirit will not be forgiven, either in this age or in the one to come.
To say that Christ does not change us and keep us is to speak against the Holy Spirit.