The law does not exist today, that is why sin does not exist.
The Apostles lived in the last generation of the law from AD30 to AD70 (from the Cross till the Temple was destroyed).
Jesus died on the cross to make the law obsolete but it was not fully removed until AD70.
In those last days of Israel, God was removing the law and bringing grace to the world. But this did not happen all on one day! It happened over a period of 40 years (one generation)
On the Cross, the law began to fade away.
– First circumcision passed away
But the believers had to fulfill the law by loving one another and not sinning (Romans 13:8-14, James 2:1-11, Galatians 5:13-15)
The believers could still sin in that generation.
Sin still existed because the law still existed.
They could lose salvation if they lived in sin (broke the law) (See James 2:1-11, Romans 8:13, 1 Thessalonians 4:3-8, Galatians 5:19-21, Galatians 6:7-10)
It is because the entire law still existed and they were expected to fulfill the law by the power of the Spirit.
Believers could lose salvation if they trusted in the ceremonial law of circumcision (Galatians 5:1-4)
But then the law passed away in AD70 when the temple was destroyed.
Hebrews 8:13 “13 By calling this covenant “new,” he has made the first one obsolete; and what is obsolete and outdated will soon disappear.”
Today, there is no law, and therefore there is no sin.
Romans 4:15 “15 because the law brings wrath. And where there is no law there is no transgression.”
Jesus fulfilled the law on the cross and removed it in AD70.
Without the law there is no sin.
The law does not even exist today.
So today, nobody is a sinner by their actions.
Today, there is no command to fulfill the law (by loving others) and therefore there is no sin.
But the world is not universally saved because everyone is born spiritually dead as descendants of Adam.
The only command today is to believe in Jesus.
The only sin today is unbelief.
Everyone needs eternal life – that is freely received by faith in Jesus and not by works.
The believer has eternal life and cannot sin.
Today a believer cannot lose salvation because we cannot sin.
This is because there is no law.
Jesus took away sin by removing the law.
Believe and receive eternal life.