The Meaning of Numbers: The Number 18
The significance of the number eighteen in the Bible comes from its symbolic meaning for bondage. After taking possession of the Promised Land, the children of Israel were in bondage to several nations and peoples before Saul was made king. Two of their enemies, Eglon the Moabite king and the Philistines (with the help of the people of Ammon) oppressed them for 18 years (Judges 3:12, 14, 10:7 - 8).
God freed the Israelites from Eglon through Ehud (who would become one of Israel's judges). He used Jephthah in the East and Samson in the South and West to free his people from the Ammonites and Philistines.
Bondage, however, can also be spiritual in nature. Jesus healed many demonically possessed or influenced people during his ministry. On one particular Sabbath, while teaching in a Synagogue, Jesus healed a woman that had a 'spirit of infirmity' which had bent her over for 18 years!
Appearances of the number eighteen
Joshua led the children of Israel into the Promised Land after the death of Moses. Seven years later, in 1398 B.C., he completes the dividing of Canaan among the Israelites. For the next 18 years, until his death at the age of 110, he serves as Israel's first Judge.
In the period preceding Israel's first human king (1398 to 1050 B.C.), a total number of 18 people served as Judges. They were Joshua, Othniel, Ehud, Deborah, Barak, Eli, Gideon, Abimelech, Tola, Jephthah, Samson, Samuel, Ibzan, Jair, Elon, Abdon and Samuel's two sons Joel and Abiah.
Of the top ten New Testament books that contain the most material from the Old Testament, the book of 1Corinthians has content from 18 books.
The most quoted or referenced Old Testament passage found in the New Testament is Psalm 110:1. It is referenced no less than 18 times (Matthew 22:44, 26:64; Mark 12:36, 14:62, 16:19; Luke 20:42 - 43, 22:69; Acts 2:34 - 35; Romans 8:34; 1Corinthians 15:25; Ephesians 1:20; Colossians 3:1 and Hebrews 1:3,13, 8:1,10:12 - 13,12:2).
A cubit, a unit of length found in the Old Testament, was the distance of a man's arm from the point of the elbow to the end of his middle finger. A cubit is roughly equivalent to about 18 inches (45.7 centimeters).
The number eighteen and bondage
This particular type of bondage is mentioned 18 times in Scripture. Its mention in Exodus 20, the chapter that first delineates God's ten commandments, is in the context of the first commandment. After the word "bondage" God commands the children of Israel not to worship other gods (Exodus 20:2 - 3).
Serving other gods places people into spiritual bondage under Satan and his demons, which God punishes with physical bondage (see Judges 2:7, 10 - 12, 14) in order for people to reconsider their ways and repent.
Additional info on the Biblical Meaning of 18
Two of the longest names in Scripture are composed of 18 letters. They are Jonathelemrechokim (in the title of Psalm 56) and Mahershalalhashbaz (the name of Isaiah's son in Isaiah 8:1, which, when translated, means 'swift is booty, speedy is prey').