In Hebrew ‘8’ is shemoneh שמונה spelled shin-mem-vav-nun-heh שמונה and has the root שמן shin-mem-nun which has a gematrical value of 300-40-50 = 390. It is the same value as the word for ‘heaven’, shemayim spelled shin-mem-yod-mem שמים = 300+40+10+50 = 390. So, circumcision is linked to heaven.