ʿAṣr prayer (Arabic: صلاة العصر) is among daily prayers in four rak'as and it can be performed after the special time of zuhr prayer until sunset [when sun disappears from the sky, but it is not dark yet].
Description of 'Asr Prayer
'Asr prayer is 4 rak'as, on the first rak'a of which after mentioning the intention and saying takbirat al-ihram, Sura al-Fatiha and another sura (not having an obligatory sajda) usually Sura al-Ikhlas is recited and then one ruku' and two sajdas are performed. Then, the person stands up for the second rak'a and continues by reciting Sura al-Fatiha and another sura and performing ruku' and sajda.
Then, tashahhud is recited in sitting position and in the third and fourth rak'as, tasbihat al-arba'a is recited and one ruku' and two sajdas are performed.
At the end, tashahhud and salam are recited.
Time of 'Asr Prayer
The time for performing 'asr prayer begins after the special time for zuhr prayer, until maghrib. This time is divided into the special time for 'asr prayer and the time common between zuhr and 'asr prayers.
The "special time" for 'asr prayer is the time enough for performing one four-rak'a prayer before sunset, when only 'asr prayer can be performed.
By ending the special time for zuhr prayer, the common time for zuhr and 'asr prayers begin, when the person can perform 'asr prayer.
Importance of 'Asr Prayer
In the Qur'an, it is ordered to establish and observe daily prayers, and 'asr prayer is one of them, "be watchful of your prayers, and [especially] the middle prayer, and stand in obedience to Allah." (Qur'an 2: 238)
Nafila of 'Asr Prayer
Nafila of 'asr prayer has eight rak'as and has to be performed before 'asr prayer and its time is from adhan of zuhr until the length of the shadow of Shakhis (a wooden stick pierced upright in the ground erected under the sun to determine the time of zuhr) reaches four seventh of the length of the stick.
Some of the Rulings about 'Asr Prayer
If someone performs 'asr prayer before zuhr prayer and notices his mistake in the middle of the prayer, should change his intention to zuhr prayer.
If someone unintentionally performs zuhr or 'asr prayer in the special time of the other, his prayer is correct.
Both men and women should recite Sura al-Fatiha and the other sura for 'asr prayer in a voiceless manner.