The Shi'ah acknowledge the five obligatory daily prayers. However, they frequently combine the Zuhr and 'Asr prayers by offering them consecutively during the time period defined by the start of Zuhr and the end of 'Asr. They also consider it permissible to combine the Maghrib and 'Isha prayers in a similar manner. This practice is in complete agreement with the Qur'an as well as authentic traditions from the Prophet (s).

Prayer timings according to the Qur'an

• Imam Fakhr al-Din al-Razi, the famous Sunni commentator on the Qur'an, wrote regarding the verse quoted (Chapter 17, Verse 78) :
  "If we interpret the darkness (ghasaq) as being the time when darkness first appears then the term ghasaq refers to the beginning of Maghrib. On this basis, three timings are mentioned in the verse: ‘the time of noon, the time of the beginning of Maghrib and the time of Fajr'. This requires that noon be the time of Zuhr and Asr, this time is shared between these two prayers. The time of the beginning of Maghrib is the time for Maghrib and 'Isha' so this time is also shared between these two prayers. This requires allowing the combining between Zuhr and Asr and between Maghrib and 'Isha' at all times. However, there is proof to indicate that combining whilst at home without any excuse is not allowed. This leads to the view that the combining be allowed when travelling or when there is rain etc."
  [Fakhr al-Din al-Razi, al-Tafsir al-Kabir, vol. 5, p. 428]

Did the Prophet (s) combine prayers?

• Ibn 'Abbas reported that the Messenger of Allah (may peace be upon him) observed in Medina seven (rak'ahs) and eight (rak'ahs), i. e. (combined) the noon (Zuhr) and afternoon (`Asr) prayers (eight rak'ahs) and the dusk (Maghrib) and night ('Isha') prayers (seven rak'ahs).
  [Sahih al-Bukhari (English translation), volume 1, book 10, number 537; Sahih Muslim (English translation), Kitab al-Salat, Book 4, Chapter 100 Combination of prayers when one is resident, hadith no. 1522]

• 'Abdullah b. Shaqiq reported: Ibn 'Abbas one day addressed us in the afternoon (after the afternoon prayer) till the sun disappeared and the stars appeared, and the people began to say: Prayer, prayer. A person from Banu Tamim came there. He neither slackened nor turned away, but (continued crying): Prayer, prayer. Ibn 'Abbas said: “May you be deprived of your mother, do you teach me Sunnah?” And then he said: “I saw the Messenger of Allah (may peace be upon him) combining the noon (Zuhr) and afternoon (`Asr) prayers and the dusk (Maghrib) and night ('Isha') prayers.” 'Abdullah b. Shaqiq said: “Some doubt was created in my mind about it. So I came to Abu Huraira and asked him (about it) and he testified to his assertion.”
  [Sahih Muslim (English translation), Kitab al-Salat, Book 4, Chapter 100
  Combination of prayers when one is resident, hadith no. 1523, 1524]

But wasn't that due to travel, fear, or rain?

Many traditions from the Prophet (s) clearly indicate that he used to combine prayers without any particular reason.

• The Prophet (s) prayed in Madinah, while residing there, not travelling, seven and eight (this is an indication to the seven Raka't of Maghrib and 'Isha' combined, and the eight Raka't of Zuhr and `Asr combined).
  [Ahmad ibn Hanbal, al-Musnad, vol. 1, page 221]
• The Prophet (s) prayed Zuhr and `Asr in combination and Maghrib and 'Isha' in combination without a reason for fear or travel.
  [Malik ibn Anas, al-Muwatta', vol. 1, page 161]

Indeed, we are even told in some traditions about the rationality behind this practice of the Prophet (s). It was for the convenience of the ummah!

• Ibn 'Abbas reported that the Messenger of Allah (s) combined the noon prayer with the afternoon prayer and the sunset prayer with the 'Isha' prayer in Medina without
  being in a state of danger or rainfall. And in the hadith transmitted by Waki' (the words are): “I said to Ibn 'Abbas: What prompted him to do that? He said: So that
  his (Prophet's) Ummah should not be put to (unnecessary) hardship.” [Sahih Muslim (English translation), Kitab al-Salat, Book 4, Chapter 100 Combination of prayers when one is resident, hadith no. 1520; Sunan al-Tirmidhi, vol. 1, p. 26]

• The Messenger of Allah (s) observed the noon and afternoon prayers together in Medina without being in a state of fear or in a state of journey. Abu Zubair said: “I
  asked Sa'id (one of the narrators) why he did that. He said: I asked Ibn 'Abbas as you have asked me, and he replied that he (the Holy Prophet) wanted that no one
  among his Ummah should be put to (unnecessary) hardship.”
  [Sahih Muslim, English translation, Kitab al-Salat, Book 4, Chapter 100 Combination of prayers when one is resident, hadith no. 1516]

Conclusion:

Combining Zuhr and `Asr prayers, and Maghrib and 'Isha' prayers, is in accordance with the Qur’an and permissible according to the sunnah of Prophet (s), besides being more convenient. The fact that this well-evidenced sunnah is not generally practiced by our Sunni brothers does not make it inapplicable in our lives. As the famous Sunni commentator of Sahih Muslim, al-Nawawi, writes:

When a practice (Sunnah) is confirmed authentic, it is not abandoned just because some, most or all people abandon it.
[al-Nawawi, Sharh Sahih Muslim, (Beirut, 1392 A.H.), vol. 8, p. 56]

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