What is the recommended supplication (Du'a) upon breaking the fast, and is it recited before or after breaking it?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah.
It is recommended (Mustahabb) for a fasting person to recite upon breaking the fast—that is, immediately after eating or drinking—the supplication: "Allahumma laka sumtu wa 'ala rizqika aftartu" (O Allah, for You I have fasted, and with Your provision I have broken my fast).
This is because our master, the Prophet (peace and blessings be upon him), used to say this. The narration was recorded by Abu Dawud with a good (Hasan) chain of transmission, albeit in a Mursal form (a narration where a Successor reports directly from the Prophet). Shaykh al-Islam Imam Ibn Hajar al-Haytami (may Allah have mercy upon him) stated: "Its Mursal status is inconsequential, as it pertains to virtuous deeds (Fada'il); furthermore, it was connected (Mawsul) through another chain of transmission." [Tuhfat al-Muhtaj, Vol.3/P.425]
It is also recommended to recite: "Dhahaba al-dhama'u wa ibtallat al-'uruqu wa thabata al-ajru in sha' Allah" (The thirst has gone, the veins are moistened, and the reward is confirmed, if Allah wills).
This was recorded by Abu Dawud with a good (Hasan) chain. Our leading jurists (Imams) have explicitly stated that it is recommended for the fasting person to combine both supplications.
Imam al-Bajuri (may Allah have mercy upon him) stated:
"And his saying following his breaking of the fast—that is, it is recommended to say: 'O Allah, for You I have fasted, upon Your provision I have broken my fast, in You I have believed, to You I have submitted, and upon You I have relied. The thirst has gone, the veins are moistened, and the reward is confirmed, if Allah wills. O You of vast bounty, forgive me. Praise be to Allah Who aided me so that I fasted, and provided for me so that I broke my fast. O Allah, grant us success in fasting, enable us to stand in night prayer during it, and aid us in it while people sleep, and admit us to Paradise in peace.'" [Hashiyat al-Bajuri, Vol.1/P.562]
Furthermore, the fasting person may supplicate with whatever good he or she wishes, for the supplication of a fasting person is answered. Al-Bayhaqi recorded on the authority of Anas ibn Malik that the Messenger of Allah (peace and blessings be upon him) said: "Three supplications are not rejected: the supplication of a parent for his child, the supplication of a fasting person, and the supplication of a traveler." And Allah Almighty knows best.
What is the ruling on kidney dialysis while fasting in Ramadan?
Kidney dialysis breaks the fast because the dialysis fluid is nutritive, as confirmed by medical experts. Additionally, it involves the entry of substances into the body cavity (jauf).
A patient undergoing dialysis must make up for that day after Ramadan. If they are unable to do so, they must pay fidyah by feeding one needy person for each day they missed.
What is the ruling on someone who is uncertain whether he omitted one of the ab‘āḍ of the prayer, such as being uncertain whether he omitted the first tashahhud?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah ﷺ.
The ab‘āḍ include the middle tashahhud and the qunūt in Fajr prayer — for which sujūd as-sahw (the prostration of forgetfulness) is prescribed if left out. Whoever is uncertain, during the prayer, whether he omitted one of these elements, should proceed on the assumption that he did not perform it, and should perform sujūd as-sahw accordingly.
It is stated in ‘Umdat as-Sālik (p. 63): "If he is uncertain... whether he omitted a specific ab‘āḍ element, or whether he performed sujūd as-sahw, or whether he prayed three or four rak‘ahs — he proceeds on the assumption that he did not do it, and performs sujūd as-sahw."
The original principle (al-aṣl) for someone uncertain about [having performed] the first tashahhud is that he assumes he did not perform it. And Allah, the Exalted, knows best.
What should a person who doubted having missed a pillar of prayer do?
All praise be to Allah, The Lord of The Worlds. The prayer of one who doubts having missed one of its pillars is valid, and nothing is due on him/her since having a doubt after offering the act of worship doesn`t undermine its validity. And Allah Knows Best.