The ruling on combining the intention of making up Ramadan with the intention of fasting 'Arafah or 'Ashura

Question:
May Allah reward you. Honorable Shaykh, a woman fasted on the Day of 'Arafah and the Day of 'Ashura with the intention of making up Ramadan. Does it count as making up Ramadan for her, or does it count as her having fasted 'Arafah and 'Ashura?

Answer:
The Messenger (peace and blessings be upon him) said: Do not mix the fast of Ramadan with the fast of the Day of 'Ashura. You must distinguish the fast of Ramadan because it is a pillar of the guidance of Islam. As for fasting the Day of 'Ashura or the Day of 'Arafah, this is a recommended practice (sunnah). You must distinguish your fasting. If she is hesitating between making it for 'Ashura or 'Arafah, or making it for Ramadan, this is not permissible, and her obligation is not discharged. May Allah reward you. Honorable Shaykh, he says. Specifying the intention is necessary; she must fast this day either as 'Arafah or as part of Ramadan. As for mixing the two intentions, this is not permissible. She should fast it as the Day of 'Arafah, for example, and make up the day she owes from Ramadan later, or she should intend it as part of Ramadan, and this is better because fasting Ramadan is obligatory, while fasting 'Ashura or the Day of 'Arafah is a recommended practice (sunnah). The obligatory is given priority over the recommended practice (sunnah). So she must specify the intention, either for this or for that. As for combining the two intentions, this is not valid.