“Circumcise … the foreskin of your heart,” G-d says in Devarim 10:16. But how the heck do you hack off the skin around your heart? And by the way, the heart doesn’t have a foreskin!
Here’s what I gather: circumcision is a mitzvah because Abraham did it, and so should we, right? On the other hand, a circumcision isn’t a child’s choice. It’s something that happens to you without your consent. I suspect if babies could talk, they wouldn’t be too keen on elective surgery.
Also, it’s unfair that men have the opportunity to perform mitzvot that women can’t. And what about transgender people or people with ambiguous genitals? Aren’t we all children of the same G-d, fair and equal? How can G-d put us in a position where one person’s ability to glorify Him/Her is above others? Seems lame to me.
Circumcising the heart resolves that issue. It tells us, metaphorically, to remove the junk that surrounds out hearts, that keeps the good stuff from coming in. Regardless of who we are, and what we have going on “down stairs”, we can equally take part in the mitzvah of circumcision by putting G-d first and peeling away the layers of our own ego that keep us from being truly made in the image of the Lord.