A man came after the Messenger of Allah ﷺ had already prayed, and he stood to pray alone. The Messenger of Allah ﷺ said, "Who will do this man a charity by praying with him?"
أن رجلا جاء، وقد صلى رسول الله ﷺ فقام يصلي وحده، فقال رسول الله ﷺ: من يتجر على هذا فليصل معه.
Daraqutni (1/276) narrated it from Yahya bin Muhammad bin Saad, who said, Umar bin Muhammad bin Hasan Asadi narrated to us, from my father, from Hammad bin Salama, from Thabit, from Anas, and he related it. Tabarani also narrated it in Awsat (7282) through the route of Umar bin Muhammad bin Hasan, in the same manner. Hafiz Haythami raised a possibility in Majma al-Zawaid (2184) that if Muhammad bin Hasan is Ibn Zabala, then he is daif. I say, this difficulty is resolved by what appears in Daraqutni's narration, that he is Asadi, and he and his father are both truthful (saduq). This is why Zaylai said in Nasb Raya (2/58), its chain is strong. I say, it is a strong corroborating witness for the hadith of Abu Saeed.It is established from Anas bin Malik that he repeated the congregational prayer in the masjid. This comes from Jaad Abu Uthman Yashkuri, who said, "We prayed the dawn prayer in the masjid of Banu Rifa, and we sat down. Then Anas bin Malik came with about twenty of his young men and said, 'Have you prayed?' We said, 'Yes.' So he ordered one of his young men, who gave the call to prayer and the call to begin, then he stepped forward and led them in prayer." Abu Yaala narrated it (4338, in the edition verified by Athari) from Abu Rabi Zahrani, who said, Hammad narrated to us, from Jaad Abu Uthman, and he related it. Bayhaqi also narrated it (3/70) through the route of Humaydi, who said, Abu Abdul-Samad Ammi narrated to us, Jaad narrated to us, and he related it, and this is the wording used. Its chain is sahih, and Bukhari mentioned it without a full chain (mu'allaq). See Fath al-Bari (2/131).There are other hadiths on this subject, but none of them are free of some criticism. Among them is the hadith of Abu Umama, that the Prophet ﷺ saw a man praying and said, "Is there not a man who will give charity to this man by praying with him?" So a man stood up and prayed with him, and the Messenger of Allah ﷺ said, "These two are now a congregation." Ahmad narrated it (22189), as did Abu Yaala in Ithaf Khayra (1746), and Tabarani in Kabir (7857), all of them through the route of Ibn Mubarak, who said, Yahya bin Ayub narrated to us, from Ubaydullah bin Zahr, from Ali bin Yazid, from Qasim, from Abu Umama, and he related it.Ubaydullah bin Zahr, with a fatha on the zay and a saakin on the ha, Damri by clientage, Afriqi, Uthman Darimi said, "All of his hadiths, in my view, are daif." Ibn Adi said, "There occurs in his hadiths material that is not corroborated." Ibn Hibban said, "He narrates fabricated material from reliable narrators." Daraqutni also declared him daif. However, Tirmidhi transmitted from Bukhari in Ilal that Bukhari deemed him trustworthy. Nasai said, "There is no harm in him." Dhahabi said in Mughni (3922), "There is disagreement about him, but he is closer to being daif. Ahmad bin Hanbal declared him daif, while Nasai said, 'There is no harm in him.'" End of quote.Also present in this chain is his teacher Ali bin Yazid, who is Ibn Abu Ziyad Alhani, the companion of Qasim ibn Abdul-Rahman. Daraqutni said of him, "Matruk (abandoned)." Abu Ahmad Hakim said, "His hadith is worthless." Nasai said, "He is not trustworthy." Hafiz applied to him the term "daif." This is why Busiri said in Ithaf, "This chain is daif. Ibn Main said, 'Ali bin Yazid Alhani, from Qasim, and from him Ubaydullah, all of these are daif.'"Among them also is the hadith of Isma bin Malik, who said, "The Messenger of Allah ﷺ had prayed Dhuhr and was sitting in the masjid when a man entered to pray. The Messenger of Allah ﷺ said, 'Is there not a man who will stand and give charity to this man by praying with him?'" Daraqutni narrated it (1/277) through the route of Fadl bin Mukhtar, from Ubaydullah bin Mawhab, from Isma bin Malik, and he related it. Zaylai said in Nasb Raya (2/58), "It is daif because of Fadl bin Mukhtar. Ibn Adi said, 'Fadl bin Mukhtar's hadiths are munkar (unrecognized).' Abu Hatim Razi said, 'He is majhul (unknown), and his hadiths are munkar, he narrates falsehoods,' as Ibn Jawzi stated in Tahqiq." End of quote.Among them also is the hadith of Salman, that a man entered the masjid while the Prophet ﷺ had already prayed. He said, "Is there not a man who will give charity to this man by praying with him?" Tabarani narrated it in Kabir, and in it is Muhammad bin Abdul-Malik Abu Jabir. Abu Hatim said, "I met him, and he is not strong in hadith." Bazzar also narrated it, and in it is Hasan bin Hasan Ashqar, who is very daif, though Ibn Hibban deemed him trustworthy. End of quote. See Majma al-Zawaid (2182).This is also the view held by a number of the companions, among them Ibn Masud, as well as a number of the successors and others. It is the position of Imam Ahmad that it is not disliked to repeat the congregational prayer in the masjid when the imam of the neighborhood has already prayed and another congregation is present. As for the masjids of marketplaces and thoroughfares, there is no disagreement regarding repeating the congregational prayer in them.