מדרש על שבת 19:3

Rabbi Chanina ben Dosa said: All who are circumcised have (excessive) pain on the third day, as it is said, "And it came to pass on the third day, when they were sore" (Gen. 34:25). They may wash || the child on the third day, when it happens to fall on the Sabbath, and all things necessary for a circumcision are permitted to be done on the Sabbath.