Sayyidah Aishah Siddiqah (may Allah be pleased with her) narrates that she heard the Prophet (peace and blessings be upon him) say: "Indeed, Allah Almighty has made five prayers obligatory upon the servants in every day and night."
Al-Tabarani recorded it in al-Mu'jam al-Awsat, and its chain is hasan (good).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 1619