What did people think bad luck was caused by?

Religious Reasons

Explanation: The belief of the number 13 was cursed or bad luck. In the Middle Ages, there were 13 people in attendance at the "Last Supper" therefore it was believed that 13 people at the gathering was a bad omen. The reasoning for that is because, Judas was the first to get up from the table at the Last Supper and he was the one to kill Jesus,  it stood to reason that the first person to get up from a table of 13 would mean that person would have bad luck.

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well first we can compare on what the slave masters ate and what the slaves ate well the masters ate fancy great food like chicken rice mash potatose and stuff like that and slaves ate well food that your not suppost to eat like the weird parts of turkey and chicken and slaves master chilled beat and eat and slaves work get beat and get little of sleep there you go