This speaks of the horrible circumstances and oppression the Israelites were living in in Egypt by comparing them to a smelting furnace. Alternate translation: "of Egypt. What happened to them in Egypt was terrible; it was as though they were living in a hot furnace" (See: [[rc://en/ta/man/translate/figs-metaphor]])
The word "voice" here is a metonym for what the speaker says with the voice, and "listen" is a metonym for "obey." Alternate translation: "Obey what I say" (See: [[rc://en/ta/man/translate/figs-metonymy]])