'Testify' in the Bible

who did testify the word of God, and the testimony of Jesus Christ, as many things also as he did see.

'I, Jesus did send my messenger to testify to you these things concerning the assemblies; I am the root and the offspring of David, the bright and morning star!

'For I testify to every one hearing the words of the prophecy of this scroll, if any one may add unto these, God shall add to him the plagues that have been written in this scroll,