As for the second issue: a person who enters the mosque after having already prayed is in one of two situations—either he prayed alone or he prayed in congregation.

If he prayed alone, the opinions are as follows:
• A group of scholars hold that he must repeat the prayer with the congregation in every case except Maghrib alone; among those who said this are Mālik and his companions.
• Abū Ḥanīfah says he repeats all the prayers except Maghrib and ʿAsr.
• Al-Awzāʿī says he repeats them all except Maghrib and Ṣubḥ (Fajr).
• Abū Thawr says he repeats them all except ʿAsr and Fajr.
• Al-Shāfiʿī says he repeats every prayer without exception.

All of them agree, in principle, that the prayer must be repeated because of the ḥadīth of Busr ibn Miḥjan, from his father, in which the Messenger of Allah—peace and blessings be upon him—said to him when he entered the mosque and had not prayed with the people:

“Why did you not pray with the congregation? Are you not a Muslim man?” He replied, “Indeed, O Messenger of Allah, but I have already prayed with my family.” The Prophet—peace and blessings be upon him—said, “When you come, pray with the people even if you have already prayed.”

The scholars then differed because this general directive might be restricted by analogy or by another textual proof. Whoever retained its full generality made it obligatory to repeat every prayer; this is the position of al-Shāfiʿī.

The view that excepts only Maghrib—held by Mālik, may Allah have mercy on him—limits the general wording by an analogy of resemblance. He argued that Maghrib is an odd-numbered (witr) prayer; if it were repeated it would come to resemble a paired (shafʿ) prayer, for the total would be six rakʿahs, and thus it would move from its own category to that of another. Such a shift, he maintained, invalidates it. This analogy is weak, however, because the closing salutation (taslīm) separates the witr prayers, and holding to the general text is stronger than restricting it by this type of analogy. Stronger still is the Kufan objection that repeating Maghrib would amount to performing witr twice, whereas the report states, “There are not two witr in one night.”

As for Abū Ḥanīfah, he said that the second performance counts as a supererogatory (nafl) prayer. If one repeated ʿAsr, it would mean offering voluntary prayer after ʿAsr, and there is a prohibition concerning that; hence he excluded ʿAsr on this basis, and Maghrib because it is witr and witr is not repeated. This is a sound analogy—provided that the Shāfiʿīs concede the second prayer to be voluntary.

Those who differentiated between ʿAsr and Ṣubḥ did so because the reports prohibiting prayer after Ṣubḥ do not vary, whereas they differ regarding prayer after ʿAsr, as noted earlier; this is the view of al-Awzāʿī.

If, however, one had already prayed in congregation, should he join another congregation? The majority of jurists hold that he does not repeat the prayer