In defending his Sabbath healing, Jesus points to circumcision. A male child was to be circumcised on the eighth day, and that requirement could fall on a Sabbath.
His argument reasons from an accepted covenant practice to the legitimacy of making an entire person whole.
Genesis 17 establishes circumcision as the covenant sign given to Abraham, while Leviticus 12:3 specifies the eighth day. Because the calendar does not avoid Sabbaths, faithful observance could require circumcision on that day. Later Jewish legal discussion explicitly treats circumcision as overriding ordinary Sabbath restrictions in the required circumstances.
Jesus notes that circumcision precedes Moses in the patriarchal tradition even though it is incorporated into Mosaic law.
The background shows that the dispute is not simply 'law versus compassion.' Jesus argues from within the logic of Torah observance.
If covenant law permits the necessary act of circumcision on Sabbath, he asks why healing a whole person should provoke anger. His challenge is to judge the Sabbath act consistently and rightly.