What does Proverbs 18:18 mean?

The exact nature of lots is unknown, but they were likely something like small pieces of wood or stone. The closest modern equivalent to casting lots is rolling dice or flipping a coin. Often these "lots" were inscribed with names, symbols, or numbers. These were placed in a receptacle or a garment, shaken, and cast. In the ancient world, these were used to solve disputes or to make close decisions. The purpose of using lots was to avoid any perception of human bias (Proverbs 16:33; Joshua 14:2; Jonah 1:7).

The term translated as "quarrels" here can also mean "controversies" or "disagreements." When two sides are strongly opposed, or the consequences of the decision are very high, the only way to reach agreement might be through something like lots, or some other "random" selection process.

Of course, even those things which happen "by chance," from the human point of view (Luke 10:31), are part of God's sovereign control (Psalm 16:5; Proverbs 16:33). Casting lots was used for selecting territories in Canaan for the tribes of Israel (Numbers 26:55; Joshua 15). It chose the scapegoat on the Day of Atonement (Leviticus16:8, 10). Lots were used to pick out priests and Levites for sanctuary service (1 Chronicles 24:5–31; Nehemiah 10:34; Luke 1:8).

Lots were even used to choose a successor to Judas, the betraying disciple who committed suicide (Acts 1:15–19). Before casting lots to determine Judas's successor, the believers prayed for the Lord's direction. Two names were advanced: Barsabbas and Matthias. "The lot fell on Matthias, and was numbered with the eleven apostles" (Acts 1:23–26).