'Witness' in the Bible

The same came as a witness, that he might testify about the light, that all might believe through him.

Most certainly I tell you, we speak that which we know, and testify of that which we have seen, and you don't receive our witness.

What he has seen and heard, of that he testifies; and no one receives his witness.

He who has received his witness has set his seal to this, that God is true.

"If I testify about myself, my witness is not valid.

This is the disciple who testifies about these things, and wrote these things. We know that his witness is true.