'Witness' in the Bible

Even as the witness of the Christ has been made certain among you:

And as for myself, brethren, when I came to you, it was not with surpassing power of eloquence or earthly wisdom that I came, announcing to you that which God had commanded me to bear witness to.

For whenever you take the bread and the cup you give witness to the Lord's death till he comes.

Yes, and we are seen to be false witnesses of God; because we gave witness of God that by his power Christ came again from the dead: which is not true if there is no coming back from the dead.