As mentioned previously, the mitzvah of circumcision alludes to our Divine service as whole. It teaches that work must be accomplished. One may not be content with the promise that ultimately “No one will ever be estranged from Him,” and thus decide that his conduct today is of no significance. For the inner connection must be revealed, and this can be accomplished only through work.
This work involves both milah, cutting the thick foreskin, and priyah, ripping open the thin membrane, which on a spiritual plane alludes to the subduing of our material desires. Afterwards, one must perform metzitzah (sucking out the blood), thus removing the excitement generated by material things from one’s body as a whole.
On the other hand, a person must appreciate that his efforts to “circumcise the foreskin of [his] heart” will have far greater effects than could be brought about through his own labor. These endeavors will lead to a revelation from above, and the fulfillment of the promise: “And G-d your L-rd will circumcise your heart,” which in a complete sense will be manifest at the time of the ultimate Redemption to be led by Mashiach; may it take place in the near future.
(Adapted from Sichos 10 Shvat, 5713)