(49) باب مَا جَاءَ فِي فَضْلِ الْمَشْىِ إِلَى الصَّلاَةِ
Narrated AbuSa'id al-Khudri:
Prayer in congregation is equivalent to twenty-five prayers (offered alone). If he prays in a jungle, and performs its bowing and prostrations perfectly, it becomes equivalent to fifty prayers (in respect of reward).Abu Dawud said: 'Abd al-Walid b. Ziyad narrated in his version of this tradition: "Prayer said by a single person in a jungle is more excellent by multiplied degrees than prayer said in congregation."
Reference: Sunan Abi Dawud 560
In-book reference: Book 2, Hadith 170
English translation: Book 2, Hadith 560