Isaiah 41:10 says: Fear thou not; for I am with thee: be not dismayed; for I am thy God: I will strengthen thee; yea, I will help thee; yea, I will uphold thee with the right hand of my righteousness.
(KJV).
The verse appears in Isaiah 41, addressed to Israel as words of assurance from God. Read it in context at Isaiah 41:10, or the full chapter at Isaiah 41.