The Meaning of Numbers: The Number 13
The number 13 is symbolic of rebellion and lawlessness. Nimrod, the mighty hunter who was 'before the Lord' (meaning he tried to take the place of God - Genesis 10:9), was the 13th in Ham's line (Ham was one of Noah's three sons who survived the flood). Thirteen represents all the governments created by men, and inspired by Satan, in outright rebellion against the Eternal.
The phrase 'valley of Hinnom' (or variation thereof) occurs in 13 places in Scripture. The valley was the scene of the evil-inspired rites of the pagan god Moloch (or Molech). The practices related to this false deity received some credibility when they were knowingly allowed by King Solomon (1Kings 11:7) in order to please his non-Israelite wives.
One way Molech was appeased and worshipped was through the sacrifice of children who, placed on the red hot arms of the idol, were burned alive. The valley's tie to fire made for an apt backdrop of the ultimate punishment unrepentant and rebellious sinners will receive in the lake of fire (Revelation 19:20, 20:9 - 10, 14 - 15).
Appearances of the number thirteen
The longest name of a book, Thessalonians, is 13 characters.
The dragon, a symbol for Satan, is found 13 times in Revelation. Satan is behind all rebellion against God.
In Romans 1 the apostle Paul lists 23 characteristics of sinful people who have a debased or reprobate mind. The thirteenth characteristic is that they are haters of God (Romans 1:28 - 32).
Haman the Agagite had a decree signed on the thirteenth day of the first month that on the thirteenth day of the 12th month all Jews in the Persian Empire were to be killed (Esther 3:7 - 9).
The destruction of Jericho is stamped with the number 13, for the city was marched around for six straight days, and on the seventh day it was marched seven times, making thirteen total.
King Solomon spent a little more than seven years building Jerusalem's temple (1Kings 6:38). He, however, spent a total number of thirteen years building a home for himself (1Kings 7:1)!
There are at least 13 famines mentioned in the Bible (Genesis 12:10, 26:1, 41:54; Ruth 1:1; 2Samuel 21:1; 1Kings 18:1; 2Kings 4:38, 7:4, 25:3; Nehemiah 5:3; Jeremiah 14:1; Luke 15:14 and Acts 11:28.
How is the number 13 related to being defiled?
In Mark 7 Jesus mentions thirteen things that defile a person. They are adulteries, fornications, evil thoughts, murders, covetousness, thefts, wickedness, licentiousness, guile, blasphemy, foolishness, pride and an evil eye (Mark 7:20 - 23).
Additional info on the Biblical Meaning of 13
Ishmael, the first physical son of Abraham (through Hagar), was circumcised (which is the cutting off of the foreskin of a penis) when he was 13 years old (Genesis 17:25) as part of the then new covenant God made with Abraham (Genesis 17:1 - 22). But this was just the start.
Abraham also had every male born in his house (numbering at least 318 individuals - Genesis 14:14), as well as all the males he owned, and any other males (whether an adult or child) he was responsible for, circumcised on the same day (Genesis 17:23 - 27)! And, even though he was 99 years old, Abraham himself also submitted to circumcision.