What is the Sharia basis of the Udhiyah?
Praise be to Allah, and peace and blessings be upon our Master, the Messenger of Allah.
The Sharia basis of the Udhiyah (sacrificial offering) is firmly established through the Quran, the Sunnah, and the Consensus (Ijma') of the Muslims:
1. Evidence from the Holy Quran
Allah the Exalted says {what means}: "And the camels and cattle We have appointed for you as among the symbols of Allah; for you therein is good." [Al-Hajj/36]. He also says {what means}: "So pray to your Lord and sacrifice [to Him alone]" [Al-Kawthar/2]. According to the most well-known scholarly interpretations of this verse, "prayer" refers to the Eid prayer, and "sacrifice" refers to the slaughtering of the Udhiyah.
2. Evidence from the Sunnah
Al-Bara' bin 'Azib (may Allah be pleased with him) narrated that the Prophet ﷺ said: "The first thing we start with on this day of ours is to pray, then we return and sacrifice. Whoever does that has followed our Sunnah, and whoever slaughters before [the prayer], it is merely meat he has provided for his family; it is not part of the ritual sacrifice in any way" [Reported by Bukhari & Muslim].
Anas (may Allah be pleased with him) narrated: "The Prophet ﷺ sacrificed two white rams with horns. He slaughtered them with his own hand, mentioned the name of Allah (Tasmiyah), and said the Takbir" [Reported by Bukhari & Muslim].
3. Evidence from Scholarly Consensus (Ijma')
The Muslims have reached a unanimous consensus on the Sharia basis of the Udhiyah, and no one among the scholars has disagreed with this. [Al-Sherbini, Mughni al-Muhtaj, Vol.6/P.122].And Allah the Exalted knows best.
What is the ruling on istinja' after urination, and is it done with water and soap or with water only?
Istinja' from urine and stool is obligatory. It is permissible to perform istinja' with water alone, or with toilet paper alone. The best way is with toilet paper then water. If one wishes to suffice with one of them, then water is better. And Allah the Almighty knows best.
Is it valid to perform the obligatory prayer while sitting?
Praise be to Allah, and peace and blessings be upon our Master, the Messenger of Allah.
Standing (Al-Qiyam) while having the ability to do so is one of the pillars (Arkan) of the prayer; the obligatory (Faridah) prayer is not valid without it. However, whoever is unable to stand may pray sitting down. As for voluntary (Nafilah) prayers, it is permissible to pray them sitting even if one is able to stand, but the one sitting receives half the reward of the one who prays standing. And Allah the Exalted knows best.
What is the ruling on the intention of fasting, where is its place, and when is its time?
The intention is a pillar of acts of worship; it is essential, and worship is not valid without it.
Its place is in the heart, and verbalizing it is recommended so that the tongue reminds the heart. Its meaning is to be determined to abstain from nullifiers of fasting during the upcoming day with the intention of worship and obedience to Allah Almighty. This meaning is naturally present in every Muslim on every night of Ramadan, so there is no need for obsessive doubts. If one says, "I intend to fast tomorrow for the sake of Allah," it removes any doubts.
Its time is from after sunset until before the true dawn.