Traditional baptismal fonts are often octagonal in shape (and sometimes also the baptismal side-chapel of a church).
There are multiple reasons for doing so. First of all the Fathers of the Church often speak about the “eight day”. As we all know, the seventh day of the creation was the Sabbath and the Day of the Lord. In the new covenant, we no longer celebrate the seventh day (Saturday), but the eight day (Sunday), since that was the day when Christ rose from the dead.
Since baptism is the beginning of new life and the resurrection from a spiritual death, the baptismal font was made in the shape of an octagon as a symbol to the eight day and the start of eternal life.
A second reason why baptismal fonts are in the shape of an octagon, has to do with the ark of Noah where only eight souls survived the flood. From early on, the Church has stressed the symbolic connection between the ark and baptism: “The ark … wherein a few, that is, eight souls, were saved by water. Whereunto baptism being of the like form, now saveth you also: not the putting away of the filth of the flesh, but the examination of a good conscience towards God by the resurrection of Jesus Christ.” (1 Pe. 3:30-21) The number eight is therefore often used in reference to baptism and those will be saved from perdition.
Finally the number eight also refers to the eight day when our Lord Jesus Christ was circumcised. Since circumcision in the Old Testament was a symbolic image of baptism, the number eight is a fitting reference to the sacrament of life.
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