Material: Made of bronze, it was always filled with water.
Spiritual meaning: Bronze means the judgment of all the sins of mankind. To bear the condemnation of all the sins of mankind, Jesus took the sins of the world upon Himself by being baptized by John. As such, the meaning of the laver is that we can be washed of all our sins by believing that all these sins of ours were passed onto Jesus with His baptism.
The priests that served in the Tabernacle also washed their hands and feet at the laver before entering the Tabernacle and thereby avoided their death. Bronze refers to the judgment of all sins, and the laver's water refers to the baptism that Jesus received from John and through which He took the sins of the world upon Himself. In other words, the laver tells us that Jesus accepted all sins passed onto Him and bore the condemnation of these sins. The water in the laver means, in the Old Testament, the blue thread of the Tabernacle, and in the New Testament, the baptism that Jesus received from John (Matthew 3:15, 1 Peter 3:21).
So the laver refers to the baptism of Jesus, and it is the place where we confirm our faith in the fact that Jesus bore all our sins, including our actual sins, and washed them away all at once through the baptism that He received from John the Baptist over 2,000 years ago.