When there is an accident, police officers will try and locate witnesses to ask them what they saw and heard. A witness's objective is not to make up something or to try and make the story better than it actually was. No, a witness is simply to state what he or she saw—plainly. Just the facts, ma'am.
That is what believers are to do. We are to give testimony to what we know is true. The apostle John wrote in his epistle, "That which we have seen and heard we declare to you" (1 John 1:3).
If you walk in fellowship with God, He will be working in your life. He will be showing you things from His Word that will help you to grow spiritually. You will find that these things will overflow, sort of like wringing out a sponge. When we are full of the things of God, it comes out because we are sharing what we know is true.
There is also a seriousness to it, however. The word testify
means to solemnly give witness. As we tell others about Christ, there is a gravity to it. Yes, we want to talk about how God loves us and will forgive us and come into a relationship with us. But the heavy part is the fact that there is a judgment, and there is a Hell for the person who rejects God's offer of forgiveness. We are to share this truth with all seriousness.
Yet in a lot of evangelistic presentations today, there is no message of Hell or judgment. We sort of edit out that part because we are afraid we might offend someone. But my concern is that if I don't include it, then I will offend God. And I would rather offend a person than God.