Tirmidhi

English Commentary:
1:
In one narration, the words ((أَلَا رَجُلٌ يَتَصَدَّقُ عَلَى هَذَا فَيُصَلِّيَ مَعَهُ)) “Is there not a man who will give charity to this one, i.e., pray with him,” have been mentioned.

2:
However, in this hadith, it is explicitly stated that the Messenger of Allah (sallallahu alayhi wa sallam) preferred prayer in congregation. For this reason, he encouraged a person who had already prayed in congregation to go and pray again with the one who came late, so that the one who came afterwards would also have his prayer in congregation. Therefore, when there are several who have been left behind, why should they not pray together in congregation? ﴿فَاعْتَبِرُوا يَا أُولِي الأَبْصَارِ﴾ (, Surah al-Hashr: 2) The very nature of the obligatory prayer (fard salah) is, in essence, congregation.

574. Commentary:
➊ The following hadith in Jami’ al-Tirmidhi is titled: «باب ما جاء فى الجماعة فى مسجد قد صلى فيه مرة» “The Explanation of Congregational Prayer in a Mosque Where Congregational Prayer Has Already Been Performed Once.” The Companions (radi Allahu anhum ajma’in), the Followers (Tabi’in), as well as Imam Ahmad and Ishaq ibn Rahwayh, hold this view. However, some scholars say that those who come late should perform their prayer individually. For example, Abu Sufyan, Ibn al-Mubarak, Imam Malik, and al-Shafi’i—most likely their perspective is that the importance of the first congregation should remain established among the people and that they should not become heedless of it. In any case, the following authentic hadith establishes the permissibility of a second congregation.
➋ Thus, Abu Bakr al-Siddiq (radi Allahu anhu) joined him in prayer. [ابن ابي شيبة بحواله نيل الاوطار : 171/3]
➌ It is permissible to appoint someone who is praying alone as the imam, even if the other person has already performed his prayer and the first person did not intend to be an imam at the beginning.