This word is used to mark two events that are happening at the same time. In this case, Paul went to Damascus during the time when he persecuted Christians.
# with authority and orders
Paul had written letters from the Jewish leaders, granting him authority to persecute the Jewish believers.
# I heard a voice speaking to me that said
Here "voice" stands for the person speaking. AT: "I heard someone speaking to me who said" (See: [[rc://en/ta/man/translate/figs-metonymy]])
# It is hard for you to kick a goad
For Paul to resist Jesus and to persecute believers is spoken of as if he were an ox kicking at the sharp stick that a person uses to prod (or "goad") the animal. It means that Paul is only harming himself. AT: "You will only harm yourself like an ox kicking a goad" (See: [[rc://en/ta/man/translate/figs-metaphor]])