'Testify' in the Bible

And he charged us to preach unto the people, and to testify that this is he who is ordained of God to be the Judge of the living and the dead.

But I hold not my life of any account as dear unto myself, so that I may accomplish my course, and the ministry which I received from the Lord Jesus, to testify the gospel of the grace of God.

Wherefore I testify unto you this day, that I am pure from the blood of all men.

having knowledge of me from the first, if they be willing to testify, that after the straitest sect of our religion I lived a Pharisee.