It wasnarrated that Ibn 'Abbas said:
"Your Prophet (ﷺ) wasenjoinedto do fifty prayers but he returned to your Lord to make(i.e.,reduce) them to five prayers." (RU)
English reference (RU): Vol. 1, Book 5, Hadith 1400 (RU)
Arabic reference (RU): Book 5, Hadith 1464 (RU)