QUESTION

When there are so many important things we don't know or understand about Jesus; why do we get to know such a personal, intimate detail about Him as his penis?  Specifically, the circumcision of the foreskin of his penis?  Why do we even get to know the exact day that the foreskin of His penis was circumcised?

Brit milah (Hebrew: בְּרִית מִילָה ) covenant of circumcision
This covenant is between G-d and the Jewish people. The Torah tells the story of G-d saying to Abraham: "I will establish My covenant between Me and you and your children after you, throughout all generations, as an everlasting covenant, to be your G-d and your children's after you ... This is My covenant which you shall keep ... every male among you shall be circumcised. And you shall be circumcised in the flesh of your foreskin; and it shall be a sign of a covenant between Me and you." (Genesis 17, 7-11).

IT'S ALL ABOUT THE BLOOD OF JESUS ~ What was so significant about this was that Jesus’ life of perfect obedience to God’s Law was set in motion, as He who was born under the Law began to redeem those under the Law (Galatians. 4:4). Here at Jesus’ circumcision, Christ shed His first precious drops of divine blood, the blood that was the price of our redemption.  It was Jesus’ first suffering for our sin, as He took on the obedience of the Law for our sake, passively keeping the Law by His parent’s obedience.  It was our sin, and the sin of Abraham and all humanity before and after him that brought this necessity upon Jesus.  Those first drops of blood Jesus shed on the eighth day were a foreshadowing of the blood He would have to shed on the cross for our sins, as drop by drop the full price of the world’s sin was drained from His bruised, dying, and then dead body.

COVENANT?

A covenant, in its most general sense, is a solemn promise to engage in or refrain from a specified action. More specifically, a covenant, in contrast to a contract, is a one-way agreement whereby the covenanter is the only party bound by the promise.  A covenant may have conditions and prerequisites that qualify the undertaking, including the actions of second or third parties, but there is no inherent agreement by such other parties to fulfill those requirements. Consequentially, the only party that can break a covenant is the covenanter ~ in this case, God.