Does undergoing an endoscopy during the day in Ramadan affect the validity of fasting?
Undergoing an endoscopic procedure during the day in Ramadan—whether through the mouth, nose, front private part, or back private part—invalidates the fast.
Whoever undergoes such a procedure must refrain from eating and drinking for the rest of the day out of respect for the sacred month and make up for that day after Ramadan.
Is it recommended (mustaḥabb) for the one offering a voluntary sacrifice (uḍḥiyyat taṭawwuʿ) to eat from its meat?
In the Name of Allah, and may peace and blessings be upon our Master, the Messenger of Allah.
It is highly recommended (Mustahabb) for the person offering a voluntary Udhiyah (sacrificial animal) to eat from its meat, but it is not an obligatory requirement (Wajib). Allah the Almighty says {what means}: "So eat of them and feed the needy who do not beg and the beggar. Thus have We subjected them to you that you may be grateful." (Al-Hajj/ 36)
"So eat of them": This directive is an encouraging recommendation, not a binding command.
The Qani’ (the needy who do not beg): Refers to a poor person who refrains from asking people for help out of dignity.
The Mu’tarr (the beggar): Refers to a poor person who explicitly asks others for assistance. And Allah the Almighty Knows Best.
Is it incumbent on a father to cover the marriage costs of his son if the latter couldn`t afford them?
The son should seek the help of his relatives in order to convince his father to do the aforesaid, and the father should make sure that his son doesn`t commit fornication through helping him to get married, and Allah will reward him for doing so.
What is the ruling of Islamic Law on supplicating with other than the transmitted (Ma'thur) supplications in prayer?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah.
It is permissible to supplicate (make du'a) during the prayer for anything from the affairs of religion or worldly life, and the prayer is not invalidated by doing so.
Shaykh al-Islam, the Imam an-Nawawi, may Allah have mercy on him, says: "Our madhhab [i.e., the Shafi'i madhhab] holds that it is permissible for a person to supplicate during it [the prayer] with anything that is permissible to supplicate with outside the prayer, from the affairs of religion or worldly life. He may say: 'O Allah, grant me wholesome sustenance, offspring, a house, and a beautiful young wife' — describing her; or: 'O Allah, free so-and-so from prison,' or 'destroy so-and-so,' and other such things — and none of this invalidates his prayer according to us. And this is also the view of Malik, ath-Thawri, Abu Thawr, and Ishaq." [Al-Majmu', Vol.3/P.454]. And Allah, the Exalted, knows best.