Dear respected Shaykh, assalamu alaikum wa rahmatullahi wa barakatuh. What is the ruling of making the intention for observing a voluntary fast at night? تبييت النية في صيام التطوع؟

Praise be to Allah, and may Allah’s peace and blessings be upon the Messenger of Allah, his family and his companions.   Wa alaikum assalam wa rahmatullahi wa barakatuh.   As to what follows:   In response to your question, we say:     The scholars have two opinions concerning voluntary fasting. A group of scholars have stated that it is compulsory for a person to make the intention for a voluntary fast at night because of the hadith of Hafsah and ‘Aishah which states, “Whoever does not have the intention of fasting from the night before, then there is no fast for him” [an-Nasai (2334)], and the hadith is general for all types of fasting. A group of scholars, and that is the opinion of the majority of the scholars are of the opinion that it is valid to observe a voluntary fast after making an intention for it during the day. Alright, so what has excluded the voluntary fasting from the ruling that is stated in the hadith of ‘Aishah and Hafsah? It has been excluded by what was transmitted by Imam Muslim in the hadith of ‘Aishah that the Prophet (peace be upon him) came to her one day and said: “Is there anything with you,” that is to eat?” Look at this chief of the children of Adam who if he wanted Allah would have turned the mountains into gold for him, and made the rivers run under his feet (peace be upon him), he is saying, “Do you have anything”, in his house. ‘Aishah said, “No”. He said, “Then I am fasting” [Muslim (1154). Thus the hadith apparently indicates that he made the intention for fasting when he could not find food, and this was during the day. Thus this indicates that it is permissible to observe an optional fast after making an intention during the day. Therefore, this hadith is an exception from the hadith which states “Whoever does not have the intention of fasting from the night before, then there is no fast for him”. Alright, is this general for an unrestricted or a restricted optional fasting, because an optional fast is of two types: an unrestricted fast and a restricted fast? An unrestricted fast is that which has no specific reason, whereas a restricted fast is the one for which a specific virtue was transmitted like fasting on the day of ‘Ashurah (the tenth of Muharram), the day of ‘Arafah, the six days of Shawwaal, Monday and Thursday, and so on. So is the ruling of making the intention for an optional fast general for an unrestricted fast and a restricted fast? The scholars have two opinions about that. Some say that the ruling is specific for unrestricted fasting, and it is compulsory to make intention in the night in order to obtain the virtues of a restricted fast.  Thus whoever wants to attain the virtues of fasting the day of ‘Ashura, or the six days of Shawwal should make an intention to fast at night. Undoubtedly this the best thing to do. However, if a person wakes up late tomorrow, just before midday and says, “There is a still a day or two from the six days of Shawwal that are remaining for me, so I want to fast today”. What is most apparent, and is the opinion of the majority of the scholars is that his fast that he made an intention for during the day is valid.