The salat has been described in some ahadith as “the pillar of religion.” Imam 'Ali (a.s.), after receiving the fatal injury by Ibn Muljim (may Allah curse him), in a part of his advice to his sons, al-Hasan and al-Husayn (a.s.) said, ”[Fear] Farewell Allah, and keep Allah in view with regardst salat, for it is the pillar of your religion. [Fear] Allah, and keep Allah in the matter of the house of your Lord (i.e., mosque): do not leave it empty as long as you live.” 
As-Sukuni narrates from Imam as-Sadiq (a.s.), “The Messenger of Allah (s.a.w.) said, 'Satan is frightened from a believer as long as he keeps up salat on time; but when he starts neglecting them, Satan becomes emboldened and tempts him to commit major (sins).'”  Yazid bin Khalifa said that he heard Imam as-Sadiq (a.s.) say, “When a person stands for salat, mercy descends upon him from the heaven to the earth and the angels engulf him, and an angel calls out: 'if this person knew what is [the reward] for the salat, he would never stop.'”
From these [few selected ahadith] we can understand the clear and obvious importance of salat in Islam. And since salat is like having audience with the Almighty Allah (as the ahadith have it that a person standing for prayer is as if he is standing in audience of the Almighty), the worshiper should approach Allah through presence of heart by not thinking or occupying his mind with anything worldly and transitory. Almighty Allah says in the Holy Qur'an: “Indeed successful are the believers who are humble in their prayers.” (24:1)
When Imam 'Ali Zaynu 'l-'Abideen (a.s.) said his salat, he used to stand “firm and motionless like a tree: nothing moves on it except what is moved by the wind.”  When the Imams, al-Baqir and as-Sadiq (a.s.), stood for their salat, “their colour would change to red and then yellow as if they were talking to someone whom they could see.” 
1. The mujtahids say that salat cannot be skipped under any circumstances. It means that it is not to be omitted whether one is travelling or at home; even if the time is running out, it is obligatory upon the Muslim, for example a traveller, to say his salat in a plane, ship, car, or a train whether stationary or moving; it could be performed any where: in the waiting room, in a public park, on the side of a road, or at the work-place, etc.
2. When it is not possible for
the traveller to say the salat in a plane or a car or a train in a standing
position, he should say it while he is seated.
3. It is permissible to ask the
airhostess about the direction of the qiblah so that she may ask the pilot
about it. If you have confidence in their information, you can rely on it even
if they are non-Muslims.
4. If a Muslim cannot do wudhu (minor ritual ablution) for the salat, then he should do tayammum instead.
5. The length of day and night differs from place to place. If the day and the night are clearly known by the rising of the sun and its setting, the Muslim should rely on the rising and the setting of the sun for determining the times for salat and fasting. This is so even if that means that the prayers have to be said more frequently shorter days or that fasting becomes lengthier shorter nights.
6. In some places the sun does not set or does not rise at all for a number of days or months. As a matter of precaution Muslims should rely on the timings of the closest city that has night and day in a twenty-four hour period. Thus, they will, pray five salats according to the times of that closest city with the intention of qurbat in general [i.e., without saying ada (prayer on time) or qadha (prayer outside its time)].
7. If it is not possible for a Muslim to determine the beginning of true dawn (fajr) or the midday or sunset for his prayers and fasting, and he has faith in the timings given by the observatories, he can rely on the same, even if the scientists running the observatories are non-Muslims-as long as you have faith in their determining true dawn or noon or sunset times.
8. For a traveller, it is
obligatory to say salat in qasr form; that is, he will recite the noon,
afternoon and night prayers only two cycles (rak'at) [instead of the normal
four rak'at] provided he travels for forty-four kilometers or more (in both
ways), starting from the last houses of his city in normal cases. 
9. Praying Friday salat with due attention to its required conditions is preferable to praying the noon salat, and is sufficient; that is, if a person says Friday prayer, he does not have to say noon prayer.
10. Praying in congregation (jama'at) is preferable to praying individually. Its preference is stronger in the dawn, sunset and night prayers. A noble hadith says: “A salat [in congregation] behind a learned scholar is like [praying] a thousand cycles; and behind a Qurayshi is like [praying] a hundred cycles.” As the number of the worshippers increases, the preference [and the reward] also increases.
Questions and Answers
1. Question: A
person used to make mistakes in the way he performed his wudhu (minor ablution)
or ghusl (major ablution). After many years, he comes to realize his mistakes.
When he inquires as how to solve his problem, he is told: “Repeat all your
prayers and perform the pilgrimage again.” Since saying all the prayers and
doing the pilgrimage again is difficult, is there a solution which would
salvage his prayers and pilgrimage performed with wudhu and ghusl that he
thought was correct? Is there such a solution as a concession to this person so
that he does not become disheartened and rebellions against religious
obligations in a society which encourages such kind of rebellion?
Question: Some people pray for years and
even perform pilgrimage, yet they do not pay khums.  Is it obligatory on them to repeat their
prayers and pilgrimage?
1. Question: If
a traveller leaves his home town immediately after the adhan of noon prayer,
i.e. without saying that prayer, and reaches his destination after sunset, has he
committed a sin? And is it obligatory on him to make up for noon prayer?
2. Question: Is
the ink that had dried [on our hands, for example] a barrier to perform wudhu
3. Question: Is
it permissible for a Muslim to involve in pleasure by continuing to watch an
entertaining movie even, though salat time is due, and then he goes to say his
prayers just before it becomes overdue (qadha)?
4. Question: Is
cream a barrier to water reaching the skin, and if so should it be removed
prior to wudhu and ghusl?
Some women let their nails grow longer than necessary for beauty. Sometimes a
nail breaks up, requiring a cover that must be placed over the broken nail.
Knowing that such a cover prevents water from reaching the nail in wudhu and
ghusl, is it permissible to use it? How should wudhu and ghusl be performed
with that cover?
When should one say his salat full (tamam) and when should one say it qasr (two
rakat instead of four)? Is the general perception about a person being resident
of a city sufficient for him to say his salat fully [in that city]?
How can we know the time of mid-night? Do 00.00 hours the point of mid-night as
it is commonly held by some people?
8. Question: A
person who believes that he will not be able to wake up for dawn prayer if he
goes to sleep, is it obligatory on him to stay awake till the time of prayer?
Is he committing a sin if he sleeps and does not wake up for dawn prayer?
How can we say our obligatory prayers in an aircraft, especially if we do not
know the direction of the qiblah taking into consideration the instability of
the floor [because the plane is in motion]?
Question: How should we say our salat in trains and
cars? Is it necessary to do prostration (sajda) on something or is it not
necessary, in that would bending of the neck be sufficient?
Question: If the time for salat has come while the
student is still on his way to the university. When he reaches the university,
he realizes that the time of salat has ended. In this case, is it permissible
for him to say salat in the car although there are places in which he could
pray, yet by going to those places he may risk becoming late [for his
Question: It happens that the time of salat sets in
while the Muslim worker is at his work-place, - noting that finding work is not
easy - thus, he finds it difficult to leave the work for salat. Sometimes he
ends up losing his job because of his insistence on saying salat. Is he allowed
to say his prayers as qadha? Or must he say them [on time], even if it leads to
him losing his job?
13. Question: Many big companies and business in the West employ large numbers of employees who work in offices about whose ownership they have no idea. So what is the ruling on:
a. Praying in those offices and using the water for wudhu?
b. If praying there is problematic, what would become of past prayers said in those places?
c. There is no problem in praying in those places nor in using the water for wudhu as long as it is not known to have been usurped.
d. If it becomes clear after saying the salat that the property was usurped, the past prayers are valid.
1. Question: If
I pray with a leather belt or a wallet made from leather of a mayta and realize
it during the salat or after finishing it but before the end of its time span
or after the ending of its time span-what would become of that prayer?
One of the famous trousers these days is the one known as jeans. It is made in
non-Muslim countries. It has a piece of leather used as a label. It is not
known whether the leather is that of an animal slaughtered Islamically or
non-Islamically-is it permissible to say salat with these trousers?
3. Question: Is
salat valid if the person uses cologne? Is cologne ritually pure?
4. Question: Is
it alright to do sajdah on concrete or on mosaic?
Some prayer-mats are made of synthetic material; is it permissible to do sajdah
6. Question: Is
it permissible to do sajdah on writing paper and on paper tissues, especially,
if is not known whether or not the raw material they are made of was from items
on which sajdah is valid?
7. Question: A
reciter of the Holy Qur'an recites a verse of wajib sajdah, on hearing it from
a cassette player, is it obligatory on us to do sajdah in this case?
 Tafsilu Wasa'ili 'sh-Shi'a, vol. 4, p. 35.
 Imam 'Ali, Nahju 'l-Balagha (ed. Subhi as-Salih), p. 422.
 Tafsilu Wasa'ili 'sh-Shi'a, vol. 4, p. 28.
 Sayyid Muhammad Hadi al-Milani, Qudatuna: Kayfa Na'rifuhum, vol. 6, p. 164 which has a special section on the prayers of Imam Zaynu 'l-'Abideen (a.s.).
 Sayyid as-Sistani, Minhaju 's-Saliheen, vol. 1, p. 193.
 “In normal cases” means other than the major metropolitan cities where going from one end to another is considered travelling.
 Translator's Note: Khums is an annual Islamic tax applied, among other things, on the savings. See the Manual of Islamic Laws or the present translator's, Khums: An Islamic Tax for details.