What is the reward of praying in the mosque?

Multiplied reward

The Prophet ﷺ said that a prayer in congregation is twenty-seven times better than a prayer alone (Sahih al-Bukhari 645). In another narration he said twenty-five times, and explained why: when a person makes wudu well and walks to the mosque only for prayer, every step raises him one degree and removes one sin. Then, while he sits waiting for the prayer, the angels keep saying, "O Allah, forgive him; O Allah, have mercy on him," as long as he doesn't break his wudu (Sahih al-Bukhari 647).

So the reward doesn't start when the imam says "Allahu akbar". It starts at your front door.

A home in Paradise

The Prophet ﷺ said that whoever goes to the mosque in the morning and the evening, Allah prepares a place of hospitality for him in Paradise each time he goes (Sahih al-Bukhari 662). He also listed among the seven people shaded by Allah on the Day of Judgment "a man whose heart is attached to the mosques" (Sahih al-Bukhari 660).

Special mosques

Some mosques carry extra reward. The Prophet ﷺ said a prayer in his mosque in Madinah is better than a thousand prayers elsewhere, except al-Masjid al-Haram in Makkah (Sahih al-Bukhari 1190), where the reward is even greater. Your local mosque in Birmingham or Chicago doesn't have that multiplier, but the 27-fold reward of congregation applies everywhere.

More than numbers

The mosque also gives things that are hard to measure: friendships, a place to ask questions, and a community that notices when you are missing. For a new Muslim, that can matter as much as the reward itself. Start with simple habits like praying two units when you enter (see What is tahiyyat al-masjid?) and dressing comfortably and modestly (see What should I wear to the mosque?).