'Testimony' in the Bible

If we receive the witness of men, the witness of God is greater; for this is God's testimony which he has testified concerning his Son.

He who believes in the Son of God has the testimony in himself. He who doesn't believe God has made him a liar, because he has not believed in the testimony that God has given concerning his Son.

The testimony is this, that God gave to us eternal life, and this life is in his Son.