Hadith: The reward of a man's prayer in congregation is twenty five times greater than that of the prayer he offers in his house or market

عن أبي هريرة رضي الله عنه مرفوعًا: «صلاة الرجل في جماعة تَضعُفُ على صلاته في بيته وفِي سُوقِه خمسا وعشرين ضِعفًا، وذلك: أَنَّه إِذَا تَوَضَّأ، فَأَحسَن الوُضُوء، ثمَّ خرج إلى المسجد لاَ يُخرِجُهُ إلاَّ الصلاة؛ لَم يَخْطُ خُطوَةً إِلاَّ رُفِعَت له بِها درجة، وَحُطَّ عَنهُ بها خطيئة، فإذا صلَّى لم تزل الملائكة تُصَلِّي عليه، ما دام في مُصَلاَّه: اللهُمَّ صَلِّ عليه، اللهم اغفِر له، اللهم ارْحَمه، ولا يزال في صلاة ما انتظر الصلاة».
[صحيح] - [متفق عليه]

Abu Hurayrah (may Allah be pleased with him) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) said: "The reward of a man's prayer in congregation is twenty five times greater than that of the prayer he offers in his house or market. That is because if he performs ablution thoroughly, then sets out for the mosque with the sole intention of praying, he will not take a step except he is raised one degree in reward, and one sin is removed from his account thereby. Then when he offers his prayer, the angels keep on supplicating Allah for him as long as he is in his place of prayer (saying): 'O Allah, Bestow Your blessings upon him; O Allah, forgive him; O Allah, have mercy upon him.' He is considered to be in prayer as long as he is waiting for prayer."
Sahih/Authentic. - [Al-Bukhari and Muslim]

Explanation

The Prophet (may Allah's peace and blessings be upon him) informs that the reward of the prayer that a man offers in congregation exceeds the reward of the prayer he offers in his home or market, i.e. the prayer which he offers alone, as inferred by comparing it to the congregational prayer, and because the prayers offered at home or in the market are performed individually in most cases. Congregational prayer exceeds the prayer one offers alone by the amount of twenty five times. His statement: "That is because," if "that" here refers to the virtue of prayer in congregation over praying alone, then this necessitates that this virtue is restricted to offering the prayer in congregation in the mosque. His statement: "Because if he," i.e. the person, if he performs ablution thoroughly, i.e. properly by doing the Sunnah acts and observes its etiquettes, then sets out in the direction of the mosque, with nothing causing him to go out but the prayer (if something else causes him to go out, or he goes out because of something else along with the prayer, then he will miss the following merits: He will not take a step except that he is raised one degree by it, and one sin is removed from his account, i.e. the minor sins involving rights of Allah, the Exalted. When he finishes his prayer, the angels continue to supplicate Allah for him, seeking mercy and forgiveness for him, as long as he is in his place of prayer, i.e. sitting therein. It is also probable that it means: as long as he remains in it (the place) even lying down, and does not invalidate his ablution. The praying person remains in prayer as long as he is waiting for the prayer," i.e. the period of time during which he is waiting for it.