# Those who curse the day–may they curse it, those who know how to wake up Leviathan
"Those who curse the day—those who know how to wake up Leviathan—may they curse the day I was born"
# Those who curse the day
"Those who know how to curse people". People who use magic to cause other people to suffer on a given day.
# those who know how to wake up Leviathan
Job is probably referring here to sorcerers and magicians. Leviathan was an animal well known in Ancient Near Eastern mythology, which was thought to be responsible for all kinds of destruction, disorder, and chaos.