In commenting on circumcision in Genesis 17, the blessed Martin Luther makes the following observation:
The mystic reason which the Master of the Sentences and other teachers adduce is passable. They maintain that circumcision was deferred to the eighth day because in the resurrection, which is signified by the eighth day, we shall be perfectly circumcised, in order that we may be free from every sin of the world.
We not only do not reject this thought, but we confirm it as godly and learned. In an allegorical sense the eighth day signifies the future life; for Christ rested in the sepulcher on the Sabbath, that is, during the entire seventh day, but rose again on the day which follows the Sabbath, which is the eighth day and the beginning of a new week, and after it no other day is counted. For through His death Christ brought to a close the weeks of time and on the eighth day entered into a different kind of life, in which days are no longer counted but there is one eternal day without the alternations of night.
This has been thought out wisely, learnedly, and piously, namely, that the eighth day is the eternal day. For the rising Christ is no longer subject to days, months, weeks, or any number of days; He is in a new and eternal life. The beginning of this life is perceived and reckoned, but there is no end. In that life the true circumcision will be carried out. At that time not only the foreskin of the heart will be circumcised—which happens in this life through faith—but the entire flesh and all its essence will be cleansed from all depravity, ignorance, lust, sin, and filth. Consequently, the flesh is then immortal.
This allegory is a prophecy that when Christ rises again there will be a spiritual, true, and perfect circumcision outside time in eternal life.
[Luther’s Works 3:140-141]
Both the baptismal font and the marble floor beneath it here at Divine Shepherd are eight sided as a reminder that we are incorporated into Christ’s death and resurrection in Holy Baptism and await with joy the final cleansing of the entire body on the Last Day.