The original rule is that a person fasting voluntarily should not break their fast without an excuse; as narrated by Abu Huraira, may Allah be pleased with him, who said that the Prophet (peace be upon him) said: "If one of you is invited, let him accept. If he is fasting, let him pray, and if he is not fasting, let him eat," in Sahih Muslim 2: 1054. However, there are legal excuses for breaking the fast in voluntary fasting: First: hospitality: it is an excuse in voluntary fasting for both the guest and the host, provided that the host is confident in making up the fast later. If the host is someone who does not accept mere attendance and is harmed by not breaking the fast, or if the guest will not be satisfied unless he eats with him and is harmed by presenting food alone, he may break his fast if he is confident in making it up later. Refer to: Al-Bahr Al-Ra'iq 2: 310, Al-Fatawa Al-Hindiyya 1: 208, Al-Durr Al-Mukhtar 2: 429, and Rad Al-Mukhtar 2: 430; as narrated by Jabir bin Abdullah, may Allah be pleased with both of them, who said: "A man from the companions of the Prophet (peace be upon him) prepared food and invited the Prophet and some of his companions. When the food was brought, one of them stepped back. The Prophet (peace be upon him) asked him: 'What is wrong with you?' He said: 'I am fasting.' The Prophet (peace be upon him) said: 'Your brother has gone to the trouble of preparing for you, and then you say: 'I am fasting.' Eat, and fast another day in its place," in Sunan Al-Daraqutni 2: 178, and others. Refer to: Al-Daraya 1: 283, and Al-Tahqiq 2: 103, and Nasb Al-Raya 2: 465. And from Abu Juhaifa, may Allah be pleased with him, who said: "The Prophet (peace be upon him) made a bond of brotherhood between Salman and Abu Darda. Salman visited Abu Darda and saw Umm Darda dressed poorly. He said to her: 'What is the matter with you?' She said: 'Your brother Abu Darda has no need for this world.' Then Abu Darda came and prepared food for him and said: 'Eat.' Salman replied: 'I am fasting.' Abu Darda said: 'I will not eat until you eat.' So he ate. When night came, Abu Darda went to pray, and Salman said: 'Sleep.' He slept, then went to pray, and Salman said: 'Sleep.' When it was the last part of the night, Salman said: 'Get up now and pray.' Salman told him: 'Your Lord has a right over you, and your soul has a right over you, and your family has a right over you, so give each one their due right.' He went to the Prophet (peace be upon him) and mentioned this to him, and the Prophet (peace be upon him) said: 'Salman has spoken the truth,' in Sahih Al-Bukhari 2: 694, and Sahih Ibn Hibban 2: 24, and its indication is that Salman, may Allah be pleased with him, was a guest of Abu Darda and broke his fast at his insistence, and the Prophet (peace be upon him) did not disapprove of him after being informed of the incident. Refer to: I'la Al-Sunan 9: 161. Second: an oath: if someone swears to divorce his wife if he does not break his fast for his guest, then the guest may break his fast voluntarily, even if the fast is a make-up fast, provided he is confident in making it up, and it is before noon; to avoid harming his Muslim brother. Refer to: Rad Al-Mukhtar 2: 430-431, and Al-Hadiyya Al-Alaiyya p. 174. Third: obedience to parents: if one of the parents forbids the child from fasting out of fear for him from illness, then it is better to obey them if he is confident in making it up, even if it is after noon until Asr. Refer to: Al-Talimat Al-Mardiya p. 174, Al-‘Inaya 2: 362, and Fath Al-Qadeer 2: 360. Fourth: obedience to the husband: it is disliked for a woman to fast a voluntary fast without her husband's permission, unless it does not harm him: such as if her husband is sick, traveling, or in a state of Ihram for Hajj or Umrah, and fasting does not weaken her during that time. If her husband breaks her fast, she must make it up with his permission or after a minor or major separation; because the initiation of voluntary fasting is valid for her, but she was prevented from continuing it due to the husband's right. If she breaks her fast, she is required to make it up. Refer to: Al-Bahr Al-Ra'iq 2: 310, Al-Hadiyya Al-Alaiyya p. 174, and Bada'i Al-Sana'i 2: 107; as narrated by Abu Huraira, may Allah be pleased with him, who said that the Prophet (peace be upon him) said: "A woman should not fast while her husband is present except with his permission, nor should she allow anyone in his house while he is present except with his permission, and whatever she spends from his earnings, half of the reward is for him," in Sahih Muslim 2: 711, and the wording is his, and Sahih Al-Bukhari 5: 1993, and Musnad Ahmad 2: 444, and it is understood in the context of voluntary fasting; so that it does not contradict his saying (peace be upon him): "There is no obedience to a creature in disobedience to the Creator," in Musannaf Ibn Abi Shayba 6: 545, and the wording is his, and Jami' Al-Tirmidhi 4: 209, and it was authenticated by Al-Suyuti. Refer to: I'la Al-Sunan 9: 163. And because he has the right to enjoy her, which he cannot do while she is fasting. Refer to: Bada'i Al-Sana'i 2: 107-108, and I'la Al-Sunan 9: 163. Fifth: obedience to the one who hired him: the hired worker who was hired by a man to serve him should not fast voluntarily without his permission; because his fasting harms the employer. However, if it does not harm him, he may fast without his permission; because his right to benefit is proportional to how much service is performed, and the service is being provided without hindrance. Refer to: Al-Bahr Al-Ra'iq 2: 310, and Bada'i Al-Sana'i 2: 107.