Psalm 66:16 Come and hear, all you who fear God, and I will tell what he has done for my soul.

This is the suggested reading when searching the word witness in my bible search engine.

It is interesting that it is suggested to witness to people who already fear God.

Luke 24:48-49 English Standard Version

You are witnesses of these things. And behold, I am sending the promise of my Father upon you. But stay in the city until you are clothed with power from on high.”

Stay in the city, in safety, until His promise clothes you in His power.

John 14:26 But the Helper, the Holy Spirit, whom the Father will send in my name, he will teach you all things and bring to your remembrance all that I have said to you.

John 15:26 But when the Helper comes, whom I will send to you from the Father, the Spirit of truth, who proceeds from the Father, he will bear witness about me.

The Holy Spirit in you will bear witness that God has done all the good things for your soul.

A vessel of light is not the light but it shines none the less.