Is the expiation for intercourse during Ramadan obligatory upon the husband alone, or upon him and his wife together?

Scholars have agreed upon the obligation of expiation (kaffarah) for a man who has intercourse with his wife during the daytime in Ramadan. However, they differed regarding the wife: if she was willing and consenting, is expiation obligatory upon her or not? The majority held that expiation is obligatory upon her. Imam Al-Shafi'i, in one of his two views, held that expiation is not obligatory upon her, but rather she only needs to make up the fast (qada'), and this is the more apparent view. This is supported by the hadith of Abu Hurairah in Al-Bukhari and Muslim, where the Prophet, peace and blessings be upon him, did not command the man to instruct his wife to offer expiation.