When did the New Testament come into effect?

Answer:

The New Testament began with the teachings of Christ. As Mark opens, "The beginning of the gospel of Jesus Christ, the Son of God" (Mark 1:1). But it was at Christ's death that history pivoted. At his death, Jesus said, "It is finished" (John 19:30) and everything changed.

"And for this reason He is the Mediator of the new covenant, by means of death, for the redemption of the transgressions under the first covenant, that those who are called may receive the promise of the eternal inheritance. For where there is a testament, there must also of necessity be the death of the testator. For a testament is in force after men are dead, since it has no power at all while the testator lives" (Hebrews 9:15-17).

"When you were dead in your transgressions and the uncircumcision of your flesh, He made you alive together with Him, having forgiven us all our transgressions, having canceled out the certificate of debt consisting of decrees against us, which was hostile to us; and He has taken it out of the way, having nailed it to the cross" (Colossians 2:13-14).

This doesn't mean that everyone was taken off-guard by a set of new laws that no one knew. Jesus had been teaching them for over three years before his death. In addition, the apostles and then other disciples received the Holy Spirit to be able to accurately teach Christ's law. "But when He, the Spirit of truth, comes, He will guide you into all the truth; for He will not speak on His own initiative, but whatever He hears, He will speak; and He will disclose to you what is to come. He will glorify Me, for He will take of Mine and will disclose it to you" (John 16:13-14). It was the teachings of the apostles and prophets that guided the early church until the time the message could be recorded.

What about those who died before the gospel reached them? God doesn't directly say, but I suspect that it is the same answer in regards to those who lived during the era of the Old Covenant and yet were Gentiles.

"For all who have sinned without the Law will also perish without the Law, and all who have sinned under the Law will be judged by the Law; for it is not the hearers of the Law who are just before God, but the doers of the Law will be justified. For when Gentiles who do not have the Law do instinctively the things of the Law, these, not having the Law, are a law to themselves, in that they show the work of the Law written in their hearts, their conscience bearing witness and their thoughts alternately accusing or else defending them" (Romans 2:12-15).

We have to remember that the reason people are lost is that they sinned. The purpose of Jesus' death and the New Law is to save people from their sins. Therefore, people who were lost in sin before the gospel reached them were still lost. That is why we realize the urgency to teach the gospel. "Therefore, knowing the fear of the Lord, we persuade men" (II Corinthians 5:11). Those who could not have heard the message will be judged by what they could have known, but the result will not be good because we have all failed to live righteously. People generally understand that stealing, murder, and even lying are wrong; and yet, people steal, kill, and lie.

The early church understood the urgency so well, that by the time Paul wrote Colossians, some 30 years after Jesus' death, Paul was able to state that the gospel had been "proclaimed in all creation under heaven" (Colossians 1:23).