Jesus clearly and unambiguously tells us that we are not to make judgments about other people’s salvation, and to emphasize his point, he says that whatever standard we use to judge others will be used to judge us (Matthew 7:1-2). Just for self-preservation purposes, that fact alone should make us the least judgmental people on the planet!
In Matthew 25:31-45 Jesus teaches about the final judgment and his entire point is that he will be the final judge, and that how he judges people will be very surprising to us. In other words, he can fully see people’s heart-attitudes and hidden behaviors, and we can’t. And so, once again, we have no business judging the salvation of others – that’s Jesus’ job.
The apostle Paul affirms Jesus’ point, and even goes so far as to say that Christians have NO business making judgments on non-Christians at all (1 Corinthians 5:12-13. Paul does go on to say that, as Christians, our sphere of “judgment” is within the church, not outside of it. But if we read this statement in its proper context, we realize that Paul is NOT saying that we are in a position to judge whether a fellow Christian is saved or not. Rather, Paul is referring to the importance of mutual accountability within the body of Christ. Our “judgment” (Paul uses the Greek word krisis) of our sisters and brothers in Jesus is meant to be an exercise of humble discernment motivated by agape-love.
In regard to people outside of the church, as Jesus, Paul and the rest of the early church show us, our job is to put on display to the world the beauty and agape-love character of Jesus Christ. Only love can transform a wounded or hardened heart. In other words, not only is non-self-righteous love the path that Jesus taught us, it is also the only path that actually changes human hearts and lives.