Quoted By:
"For I am not ashamed of the gospel of Christ: for it is the power of God unto salvation to every one that believeth; to the Jew first, and also to the Greek." -Romans 1:16
The way you witness to ANYONE, is with the GOSPEL (defined in 1st Corinthians 15:1-4 as Christ's death, burial and bodily resurrection). We are ALL sinners deserving of hell-fire. Jesus Christ (the Son of God) paid for our sins with His blood; Jesus DIED; Jesus was BURIED and Jesus ROSE from the dead for our justification.
All we need to do for salvation is to trust upon Jesus Christ by faith to forgive our sins (Romans 3:10,23;5:8;6:23;10:9-13). Acts 10:43 states, "To him give all the prophets witness, that through his name whosoever believeth in him shall receive remission of sins."
The way to witness to ANYONE is to simply present the plain truth of the Gospel of Jesus Christ to them. If a person doesn't want to be saved after having the simple Gospel, then they don't want to be saved. There's no wisdom of words to convince the skeptic of the truth—the Gospel is what it is. If a man will not obey the simple Gospel, then he will not listen to the wisdom of words... "lest the cross of Christ should be made of none effect" (1st Corinthians 1:17).
Witnessing is not arguing religion with people. But some religious people have come to Christ right away when they heard the plain Gospel. A person who wants to be saved WILL trust Christ immediately, you do not need to argue anything with them. A person who wants to DEBATE religion has already rejected Christ in their heart and is now defending their unbelief.
Even if you prove them dead wrong with the Scriptures, they will still hold onto their unbelief (Mark 7:6-9; Luke 16:31). There are people all over the world who want to argue religion. We do NOT need to debate with them; but rather, just keep giving them the simple Gospel of Jesus Christ. The POWER of God which brings salvation is the GOSPEL itself, and not our cleverly worded arguments.
