The greatest witness is a life fully lived fixed on Jesus.
“Acts 7:48-60 – However, the Most High does not dwell in houses made by human hands; as the prophet says:
‘Heaven is My throne,
And earth is the footstool of My feet;
What kind of house will you build for Me?’ says the Lord,
‘Or what place is there for My repose?
‘Was it not My hand which made all these things?’
“You men who are stiff-necked and uncircumcised in heart and ears are always resisting the Holy Spirit; you are doing just as your fathers did. Which one of the prophets did your fathers not persecute? They killed those who had previously announced the coming of the Righteous One, whose betrayers and murderers you have now become; you who received the law as ordained by angels, and yet did not keep it.”
Now when they heard this, they were cut to the quick, and they began gnashing their teeth at him. But being full of the Holy Spirit, he gazed intently into heaven and saw the glory of God, and Jesus standing at the right hand of God; and he said, “Behold, I see the heavens opened up and the Son of Man standing at the right hand of God.” But they cried out with a loud voice, and covered their ears and rushed at him with one impulse. When they had driven him out of the city, they began stoning him; and the witnesses laid aside their robes at the feet of a young man named Saul. They went on stoning Stephen as he called on the Lord and said, “Lord Jesus, receive my spirit!” Then falling on his knees, he cried out with a loud voice, “Lord, do not hold this sin against them!” Having said this, he fell asleep.”