When Job finally spoke after seven days of silence, what did he curse?

Answer: The day of his birth

Job opened his mouth and cursed the day of his birth: "May the day of my birth perish."

“After this, Job opened his mouth and cursed the day of his birth. And this is what he said: “May the day of my birth perish, and the night it was said, ‘A boy is conceived.’”— Job 3:1-3 (BSB)