This can be stated in active form. Alternate translation: "For Isaiah the prophet was speaking of John the Baptist when he said" (See: [[rc://en/ta/man/translate/figs-activepassive]])
This can be expressed as a sentence. Alternate translation: "The voice of one calling out in the wilderness is heard" or "They hear the sound of someone calling out in the wilderness"
"Get the road ready for the Lord." Doing this represents being prepared to hear the Lord's message when he comes. People do this by repenting of their sins. Alternate translation: "Prepare to hear the Lord's message when he comes" or "Repent and be ready for the Lord to come" (See: [[rc://en/ta/man/translate/figs-metaphor]] and [[rc://en/ta/man/translate/figs-explicit]])