The Egyptians were the first to develop a superstition for the number thirteen, but for them the number brought good luck. They believed that there were twelve steps on the ladder to eternal life and knowledge and to take the thirteenth step meant going through death into everlasting life. Thirteen, for the Egyptians, was associated with immortality.

It was in Roman times that the number thirteen became associated with ill omens, particularly those bringing death and destruction.

For Christians, the number thirteen also brought bad luck. The superstition stems from the Last Supper where Judas Iscariot became the thirteenth guest to sit at the table and would later betray Jesus, leading to his crucifixion. Still to this day it is considered very bad luck for thirteen people to sit down for dinner together. It is believed that one of the dinner guests will die within the year.

Norse mythology also has a superstition surrounding thirteen at a dinner table and the bad luck that ensues. In fact, it is believed that the Christian story of the Last Supper may find its origin in this particular myth. Apparently twelve deities sat down for a meal at a gods’ feast only to have Loki, the god of mischief and disorder, come along and crash the party. He rose the number to thirteen, causing one of the gods to die during the meal.

The number was adopted by witches for their covens, which always number thirteen.
Still, to this day, the superstition lives on.
Most hotel chains have no room number thirteen and many skyscrapers are without a thirteenth floor.
Book results for the number thirteen in Ancient Egypt

The Literature of Ancient Egypt: An Anthology … – by William Kelly Simpson – 628 pages
The Oxford History of Ancient Egypt – by Ian Shaw – 559 pages
Historical Deception: The Untold Story of … – by Moustafa Gadalla – 356 pages