قوله ﷺ ومس الختان الختان فقد وجب الغسل قال العلماء معناه غيبت ذكرك في فرجها وليس المراد حقيقة المس وذلك أن ختان المرأة في أعلى الفرج ولا يمسه الذكر في الجماع وقد أجمع العلماء على أنه لو وضع ذكره على ختانها ولم يولجه لم يجب الغسل لا عليه ولا عليها
المنهاج في شرح صحيح مسلم للنووي كتاب الحيض باب بيان أن الجماع كان في أول الاسلام لا يوجب الغسل إلا أن ينزل المني وبيان نسخه وأن الغسل يجب بالجماع
Regarding His (SAW) words “and the circumcised part touches the circumcised part, then washing is obligatory” : The scholars have said that this means that you make your penis disappear in her vagina. The intended meaning is not necessarily touching, since the woman’s circumcised part is above the vagina, and the penis does not touch it during sex. And the scholars are in agreement that if he puts his penis on her circumcised part, but does not make it penetrate, washing is not obligatory, neither for him nor for her.
Al-Nawawi, Al-minhaj fi Sharh Sahih Muslim [Open Path in Exposition of Sahih Muslim], The book of menstruation, Section: substantiating that in sex at the beginning of Islam, washing [ghusl] was not obligatory unless semen was discharged, and substantiating that this was abrogated and that washing is always obligatory upon sex