Saint Francis of Assisi said, "Preach the Gospel to everyone and use words if necessary." What a profound statement! I believe he was saying that a living example of the Gospel is more effective than words. Some people may argue with you about doctrine or the interpretation of Scripture, but unless they believe you're a liar, they can't argue with your testimony.
In John 10:37-38, Jesus said,
"If I do not the works of my Father, believe me not. But if I do, though ye believe not me, believe the works: that ye may know, and believe, that the Father is in me, and I in him."
And in Mark 16:17-18, we read what Jesus spoke to His disciples after commanding them to go into all the world and preach the Gospel.
"And these signs shall follow them that believe; In my name shall they cast out devils; they shall speak with new tongues; They shall take up serpents; and if they drink any deadly thing, it shall not hurt them; they shall lay hands on the sick, and they shall recover."
