לע"נ הרה"צ ר' יחזקאל אליהו בן הרה"צ ר' יהושע
Why wasn't Avraham Avinu born with a bris milah as were Adam and Noach??
The answer may be based on the Zohar Hakadosh that in order to being down Divine blessing it is not enough to THINK but rather one must ACT. So it was critical that Avraham do the ACT of bris milah and not just have one at birth.
The question is that according to the Zohar the עיקר are always one's thoughts and actions are only secondary, so how does this square with his principal that one must perform an act in order to merit Divine blessing??
The Heilige Avnei Nezer made the distinction ["חילוק" in Yeshivish-eze] that in order to change things for the better in the higher worlds one must have the proper thoughts and feelings. But in order to bring the blessings down to planet Earth one must perform an action. A חילוק that is kissable!!
I think that there is a strong logical basis for this distinction. The upper worlds are purely spiritual and therefore require a spiritual initiative on our part to make changes. This world [called in Kabbala עולם העשייה] is a world where what matters most is concrete action [try THINKING about eating but not actually eating and see how long you last...] and thus to bring bounty down to this world one must perform actions.