en_tn_condensed/act/28/26.md

The Holy Spirit spoke well through Isaiah the prophet to your fathers. He said, 'Go to this people and say, "By hearing you will hear, but not understand; and seeing you will see, but will not perceive

This has quotations within quotations. You can translate one of the inner quotations as an indirect quotation, or you can translate two of the inner quotations as indirect quotations. Alternate translation: "The Holy Spirit spoke well through Isaiah the prophet to your forefathers when the Spirit told Isaiah to tell them that they will hear but will not understand; and they will see but they will not perceive" (See: rc://en/ta/man/translate/figs-quotesinquotes)

By hearing you will hear ... and seeing you will see

The words "hear" and "see" are repeated for emphasis. "You will listen carefully ... and you will look intently"

but not understand ... but will not perceive

Both of these phrases mean basically the same thing. They emphasize that the Jewish people will not understand God's plan. (See: rc://en/ta/man/translate/figs-parallelism)