Salah (Prayer) Is Made Obligatory (Chapters 3-15, practical rules about prayer are best expressed in the form of fatwa.)

“I once asked abu Ja‘far (a.s.), about how much of Salah (prayer) Allah, the most Majestic and Glorious, has made obligatory. He (the Imam) said, ‘During one day and night five prayers are made obligatory.’ I then asked, ‘Has He named and explained them in His book?’ He replied, ‘Yes, Allah, the most High, has said to His Holy Prophet (sw), “Perform prayer after the sun declines to the west, on midday until the darkness of the night.” (17: 78). The sun declines on midday. There are four prayers between midday and the darkness of the night. Allah has named, explained and timed them. Darkness of night is in midnight. He, most Blessed, most High has then said, “...and the recitation (performing prayer) at dawn and recitation at dawn was witnessed (attended by the angels of the day and those of the nights).” These are five prayers.
Allah, the most High, said about this issue, “Perform prayer on both ends of the day, [which is sunset and morning], and in a part of the night.” (11:114) This is al-Isha’ prayer. He, the most High has said, “Preserve prayer especially the middle prayer.” (2:239) Middle prayer is al-Dhuhr prayer which is the first prayer the Messenger of Allah (sw) performed. It is in the middle of two prayers during the day, the morning and al-‘Asr prayer. In some of the recitations it is said, “Preserve Salawat (prayers) and the middle prayer.” Middle prayer is al-‘Asr prayer.’
About the words of Allah, “Stand up praying before Allah,” he (the Imam) said, ‘This verse was revealed on Friday when the Messenger of Allah (sw) was on a journey. The Messenger of Allah (sw) prayed before Allah on Friday and left it in that condition during a journey or when at home. For those at home he added two Rak‘ats. He reduced two Rak‘at which the Holy Prophet (sw) had added on Friday for people when at home, because of the two sermons which a prayer leader delivers. Those who perform Friday prayer without congregation, they perform it four Rak‘at like al-Dhuhr prayer in other days.’”

“Abu Ja‘far (a.s.), has said, ‘Of Salah (prayer) Allah has made ten Rak‘at obligatory on His servants. In such Salah (prayer) there are the recitations; thus, conjectures, mistakes in such Salah (prayer) are not acceptable. The Messenger of Allah added seven Rak‘ats in which conjectures, mistakes are dealt with according to certain rules, but there are no recitations in them.’”

“‘Abu Ja‘far (a.s.), has said, ‘Allah has made Salah (prayer) obligatory. The Messenger of Allah has established ten kinds of traditions in Salah (prayer): Salah (prayer) at home and during a journey. Salah (prayer) due to fear is of three kinds. There is Salah (prayer) because of sun eclipse and moon eclipse. There is Salah (prayer) of the two ‘Id. There is Salah (prayer) for rain and (lastly) Salah (prayer) for a deceased.’”

“About the words of Allah, most Majestic, most Glorious, ‘Salah (prayer) in Mawqut (with certain timing) form was written on believers’ abu Ja‘far (a.s.), has said, ‘it means obligatory.’”

“I once asked abu Ja‘far (a.s.), about what is obligatory in Salah (prayer). He (the Imam) said, ‘Time, al-Tahur (cleansing), facing al-Qiblah (al-Ka‘bah), paying attention, al-Ruku‘, al-Sujud and praying. The rest are optional in an obligatory duty.’”

“Abu ‘Abd Allah (a.s.), has said, ‘Salah (prayer) has four thousand limits (rules).”’ “In another Hadith it is said that in Salah (prayer) there are four thousand doors (chapters).”

“Abu Ja‘far (a.s.), has said, ‘There are ten Rak‘at in Salah (prayer). There are two for al- Dhuhr, two for al-‘Asr, two Rak‘at of Morning, two Rak‘at of al-Maghrib and two Rak‘at of al-‘Isha’ al-Akhirah. In these many of Salah (prayer) conjectures (mistakes) are not acceptable. If one faces conjectures in such Salah (prayer), he performs it again. They are Salah (prayer) which Allah, most Majestic, most Glorious, made obligatory on believers in al-Quran. He (Allah) delegated Muhammad (a.s.), and he (the Holy prophet) increased seven Rak‘at. They are of Sunnah and have no recitations. They have Tasbih (Allah is free of all defects), Tahlil, (no one deserves worship except Allah) Takbir (Allah is great beyond description), and prayer. Conjectures in these Rak‘at are (dealt with according to certain rules). The Messenger of Allah increased two Rak‘at for those at home in al- Dhuhr, al-‘Asr, al-‘Isha’, al-Akhirah and one Rak‘at to al-Maghrib for those at home as well as for those on a journey.’”

“Abu ‘Abd Allah (a.s.), has said, ‘Acts of Salah (prayer) fall in three categories; They are Tahur (cleansing), Ruku‘ (bowing down on one’s knees), and Sujud (prostration).”’