פירוש על קידושין 71:4

The gezerah shavah is needed so that we can derive that the address in the beginning of Leviticus, “Speak to the sons of Aaron” refers to the whole passage, including that about making a bald spot. If we did not have the gezerah shavah we might have thought that women priests (daughters of priests) are prohibited from making a bald spot and that the exclusion of women refers only to the first few mitzvoth in the passage.