Joshua 24:22-23 And Joshua said unto the people, Ye are witnesses against yourselves that ye have chosen you the LORD, to serve him. And they said, We are witnesses. Now therefore put away, said he, the strange gods which are among you, and incline your heart unto the LORD God of Israel.
Isaiah 43:10,12 Ye are my witnesses, saith the LORD, and my servant whom I have chosen: that ye may know and believe me, and understand that I am he: before me there was no God formed, neither shall there be after me. … I have declared, and have saved, and I have shewed, when there was no strange god among you: therefore ye are my witnesses, saith the LORD, that I am God.
Acts 1:8 But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judaea, and in Samaria, and unto the uttermost part of the earth.
John 4:24 God is a Spirit: and they that worship him must worship him in spirit and in truth.