Giving Witness to the True Church of Christ
"You are my witnesses." These words were addressed by the Lord to His people, Israel, through His prophet Isaiah (Is. 43: 10.12). Witnesses to what or to whom? Witnesses to the true God, who Himself attests, gives witness, that He is the LORD, the God of Israel, the true God.
His people too can give this testimony (witness), because they have come to know that their God, the LORD, is truthful, and the things He declared became true. Let those who believe in the false gods dare to witness to their gods. They can't! Because their gods cannot prophesy, they cannot predict the future: that's a fact! Whereas those who are His, His elect, His faithful servants, the people of Israel, can give this attestation. The LORD had foretold the redemption of His people from servitude, and He rescued them. He announces beforehand the things which are to come. Therefore they are in a position to know that He is the only true God. They can, and indeed are, His witnesses!
Similarly in the new era of salvation, the LORD Himself speaks:
Then He opened their minds to understand the scriptures, and He said to them,
As the old Israel bore witness to their God from the things that happened to them, so the new Israel, the Church, bears witness to the things they have experienced with the true God in the flesh.
The Apostles were given this charge before the Ascension of the Lord to heaven, "But you will receive power when the Holy Spirit has come upon you; and you will be my witnesses in Jerusalem, in all Judea and Samaria, and to the ends of the earth" (Acts 1:8). "You are my witnesses," says the LORD. These words are addressed to all of us.
Scriptural References about being a "Witness"
"You are my witnesses, says the LORD, and my servant whom I have chosen,
so that you may know and believe me and understand that I am He" (Is. 43:10)
Stand by the road, and look, and ask for the ancient paths,
where the good way is; and walk in it, and find rest for your souls" (Jer. 6:16)
Go into all the world and proclaim the gospel to the whole creation" (Mark 16:15)
I was sent to this purpose [to preach the Good News]" (Lk. 4:43)
You are witnesses of these things" (Lk. 24:48)
As You sent me into the world, so I have sent them into the world" (John 17:18)
As the Father has sent me, even so I send you" (John 20:21)
This is the disciple who is bearing witness to these things, and who has written these things; and we know that his testimony is true" (John 21:24)
You will be my witnesses... to the ends of the earth." (Acts 1:8)
... become a witness with us to His resurrection" (Acts 1:22)
We are witnesses to these things, and so is the Holy Spirit whom God has given to those who obey him" (Acts 5:32)
...chosen by God as witnesses" (Acts 10:41, cf. 13:31)
He has not left Himself without a witness" (Acts 14:17)
Do not be afraid, but speak and do not be silent; for I am with you." (Acts 18:8-10)
You will be His witness to all the world of what you have seen and heard" (Acts 22:15)
I send you to open their eyes" (Acts 26:18)
That the world may turn from darkness to light and from the power of Satan to God" (Acts 26:18)
It is that very Spirit bearing witness with our spirit" (Rom. 8:16)
But how are men to call upon Him whom they have not believed? And how are they to believe in Him of whom they have never heard? And how are they to hear without a preacher? And how can men preach unless they are sent? As it is written, 'How beautiful are the feet of those who preach Good News!'" (Rom. 10:14-15, quoting Is. 52:7)
...surrounded by so great a cloud of witnesses" (Heb. 12:1)
Always be ready to make your defense to anyone who demands from you
an accounting for the hope that is in you" (1 Pet. 3:15)
a witness of the sufferings of Christ" (1 Pet. 5:5)
Witnessing to "the Faith once delivered to the Saints" (Jude 3)