John Gill Commentary Isaiah 43:10

"Ye are my witnesses, saith Jehovah, 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." — Isaiah 43:10 (ASV)

You are my witnesses, says the Lord
The people of Israel, who could testify that the Lord had foretold their affliction in Egypt, their coming from there, and settling in the land of Canaan, many hundreds of years before they came to pass, and which were exactly fulfilled; (Acts 1:8)

: and my servant whom I have chosen ; and so the apostles of Christ, and ministers of the word, and all Christian people in all nations, are witnesses of the prophecies concerning Christ, his birth, miracles, obedience, sufferings, death, resurrection, ascension to heaven, and session at the right hand of God, all which are exactly accomplished, : meaning either the Prophet Isaiah, or the prophets in general; or rather the Messiah. So the Targum, ``and my servant the Messiah, in whom I am well pleased;'' and who is called the faithful witness, (Revelation 1:5) (3:14), and to whom the characters of a servant, and the Lord's chosen, well agree, (Isaiah 42:1)

: that you may know and believe me, and understand that I am he ; by which testimonies and evident proofs of deity, from the prediction of future events, and the accomplishment of them, you may have a competent knowledge, a firm persuasion, and a clear perception of this important truth, that the God of Israel, and of all true Christians, is the one only Lord God:

: before me there was no God formed, neither shall there be after me ; intimating that idols were formed by the hands of men, and yet none of these were formed before him, and therefore could make no pretensions to deity, or to an equality with him; nor should any be formed afterwards, that could be put in competition with him. In short, the sense is, there is no other god beside him; as the Targum, Septuagint, and Arabic versions render it.