“It provides evidence that one who is making up a fast may break it and then make up another day in its place, even though it contains the aforementioned point of criticism. Rather, the proof is required of whoever maintains that the person making up a fast may not break it.”
I say: First, the hadith contains nothing to support his claimed permissibility. The command to make up the fast does not entail that breaking it was permissible, as is clear, Allah willing. Do you not see that, by consensus, it is impermissible to break a Ramadan fast through sexual intercourse? Yet the Prophet, may Allah bless him and grant him peace, ordered the one who broke it in that manner to make up a day in its place, along with an expiation. This is established through the combined strength of its chains, as I have demonstrated in Sahih Abi Dawud (2073). For this reason, al-Hafiz deemed it strong, and al-Shawkani himself followed him in al-Nayl (4/184–185) and al-Sayl (2/120–121). Thus, if Umm Hani had broken a make-up fast, his ordering her to make it up would not mean that what she had done was permissible—let alone when the fast she broke was voluntary.
Second, in a narration recorded by al-Tirmidhi and others, she said: “I have sinned, so seek forgiveness for me.” He said: “What is that?” She said: “I was fasting, then I broke my fast.” He said: “Was it a make-up fast that you were observing?” She said: “No.” Since she herself acknowledged what she believed to have been her wrongdoing, there was no occasion for him to reproach her for breaking her fast—even had it been a make-up fast. Nothing remained but to explain to her that she was obliged to repeat it, and this is what the hadith indicates. Abu Dawud added in one narration after the foregoing: “It does not harm you if it was voluntary.” Its clear implication is that it would harm her if it were a make-up fast. This is clear, Allah willing.
Third, the evidence is the consideration of the basic principle: just as it is impermissible to invalidate a Ramadan fast without an excuse, likewise it is impermissible to break a make-up fast. Whoever differentiates between the two must provide the evidence.