The prayers were prescribed upon the Prophet ﷺ on the night he was taken on the night journey as fifty, then they were reduced until they were made five. Then a voice called out, "Muhammad, the word with Me is not changed, and you shall have for these five the reward of fifty."
حدثنا عبد الرزاق أخبرنا معمر عن الزهري قال
فرضت على النبي ﷺ الصلوات ليلة أسري به خمسين ثم نقصت حتى جعلت خمسا ثم نودي يا محمد إنه لا يبدل القول لدي وإن لك بهذه الخمس خمسين