In the old days of raising cattle when there were no fences cattle free ranged on vacant land. Periodically the ranchers would gather their cowboys and chuck wagons and gather all the cattle and separate them based upon their branding mark. They would also gather up the unbranded calves and see how they paired up with their mommas and receive that same branding mark to identify which rancher they belonged to.
God also marks his people.
Under the Law of Moses that mark was circumcision. It wasn’t a branding mark that could easily be viewed from horseback. It was a private personal mark that was only viewed by its recipient. I mean if God wanted everyone to see it he could have had an ear notched or some other visible mark.
Let me suggest that the mark was for the recipient to remind him of who he belonged to.
Contrast that with how God marks his people today. Ephesians 1:13-14 and 2 Corinthians 1:21-22 state that he seals (marks) us with his Holy Spirit. Other scriptures suggest that happens once we have been cleaned in the waters of baptism.
Look at the similarities and differences.
Circumcision is a physical mark on a new born sinless baby (male only) that only the recipient can see. Perhaps as a reminder that he belongs to God.
Sealing with the Holy Spirit is an inward mark given to those who have been washed clean in the waters of baptism both male and female. It is a mark of ownership and provides a level of protection against Satan who dares not to trespass.
Sealing with the Holy Spirit is far far superior to physical circumcision because it changes us inwardly and helps us “walk by the Spirit” so we can grow into the image of Jesus Christ. Circumcision can't do that.
Even in a day of fencing cattle ranchers still mark their cattle to identify them and prevent theft. But ranchers don’t have much of a relationship with their cattle they all still go to slaughter.
God marks his people today and makes his home within them. If you haven’t been marked by God you belong to Satan and during the great round up you could be pastured in Hell.
God is waiting to put his mark on you don't neglect it.