Nafi‘, on Ibn ‘Umar’s authority, reported the Prophet as saying, “If anyone dies when fasting in the month of Ramadan has been unfulfilled by him, a poor man should be fed on his behalf in place of every day.”
Tirmidhi transmitted it, saying that correctly this goes no farther back than Ibn ‘Umar.
Malik said he heard that Ibn ‘Umar used to be asked whether one might fast or pray on behalf of another, and reply, “One may neither fast nor pray on behalf of another.”
Mu'adha al-‘Adawiya said that when she asked ‘A'isha why one who has been menstruating must make up for her fast but not for her prayer, she replied, “That happened to us, and we were ordered to make up for the fast, but were not ordered to make up for the prayer.”
