“A man’s prayer with another man is more meritorious than his prayer alone, and his prayer with two men is more meritorious than his prayer with one. The greater the number, the more beloved it is to Allah.” (1)
For this reason, according to one of the two reports of his view, Imam Ahmad recommended that, when the dawn prayer was delayed until it grew light, it be offered at that time for the sake of a larger congregation, even though offering it while it was still dark was better.
Thus, scriptural evidence and consensus establish that a less preferable time may have a particular advantage that sometimes makes performing the act at that time better.
As for the midmorning prayer, it was not peculiar to ‘Umar. Rather, it is established in the two Sahīh collections that Abū Hurayrah said:
“My beloved friend, may Allah bless him and grant him peace, advised me to fast three days (2) of every month, to offer two units of the midmorning prayer, and to offer the Witr prayer before going to sleep.” (3)
(1) The hadith narrated by Ubayy ibn Ka‘b, may Allah be pleased with him, appears in Sunan Abī Dāwūd, 1/151–152 (Book of Prayer, chapter on the merit of congregational prayer). Its wording there is: “The Messenger of Allah, may Allah bless him and grant him peace, led us in the dawn prayer one day, then asked, ‘Is so-and-so present?’ They replied, ‘No.’ He asked, ‘Is so-and-so present?’ They replied, ‘No.’ He said, ‘These two prayers are the most burdensome prayers for the hypocrites. If you knew what reward they hold, you would attend them even if you had to crawl on your knees. The first row is like the row of the angels; if you knew its merit, you would race to join it. A man’s prayer with another man…’” [The hadith continues.] It also appears in Sunan al-Nasā’ī, 2/104–105 (Book of Leading the Prayer, chapter on a congregation consisting of two people), and al-Musnad (al-Halabī edition), 5/140. Al-Albānī graded the hadith authentic in Sahīh al-Jāmi‘ al-Saghīr, 2/254–255.
(2) Ayyām (days) is omitted in (س) and (ب).
(3) The hadith narrated by Abū Hurayra, may Allah be pleased with him, appears in al-Bukhārī, 3/41 (Book of Fasting, chapter on fasting the white days…). An abridged version also appears there, 2/57 (Book of Night Prayer, chapter on offering voluntary prayers two units at a time). The complete hadith appears in Muslim, 1/499 (Book of Travellers’ Prayer and Its Shortening, chapter on the recommendation to offer the midmorning prayer…), and Sunan Abī Dāwūd, 2/89 (Book of Witr, chapter on offering Witr before sleeping). The hadith also appears in Sunan al-Nasā’ī and Musnad Ahmad.