John Lightfoot on John 7:22

[Ye on the sabbath day circumcise a man.] They do all things that are necessary towards circumcision on the sabbath day. "R. Akibah saith, Any work that may be done on the vespers of the sabbath must not be done on the sabbath; but circumcision, when it cannot be done on the vespers of the sabbath, may be done on the sabbath day."

"Danger of life nulleth the sabbath: circumcision also, and its cure, nulleth the sabbath."

But as to this matter, they distinguish in Bereshith Rabba: "Jacob of Nabor taught us in Tsur: It is lawful to circumcise the son of a stranger on the sabbath day. R. Haggai heard this, and sent to him saying, Come and be disciplined," &c. And a little after; "R. Haggai saith to him, Lie down [to take discipline] and I will teach you. If a heathen come to you, and say, I would be made a Jew, so that he would be circumcised on the sabbath day, or on the day of Expiation, will we, for his sake, profane those days? Do we ever profane those days either of the sabbath, or Expiation, for any other than one born of an Israelitess only?" We meet with the same also in Bemidbar Rabba, and Midras Coheleth.

Let us look a little into the way of Christ's arguing in this place: to me it seems thus: "Moses, therefore, gave you circumcision, that you might rightly understand the nature of the sabbath: for, I. Circumcision was to be observed by the fathers before Moses, punctually on the eight day. II. Now, therefore, when Moses established the laws about the sabbath, he did by no means forbid the work of circumcision on the sabbath, if it happened to be the eighth day. III. For this did Moses give and continue circumcision among you, that you might learn from hence to judge of the nature of the sabbath day. And let us, therefore, argue it: If by Moses' institution and allowance it was lawful, for the advantage of the infant, to circumcise him on the sabbath day, is it not warrantable, by Moses' law, for the advantage of a grown man, to heal him on the sabbath day? If it be lawful to wound an infant by circumcision, surely it is equally, if not much more, lawful to heal a man by a word's speaking."