It is narrated from al-Sa'ib bin Yazid (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "My Ummah will always remain upon the (sound) fitrah as long as it offers the Maghrib prayer before the stars appear."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2108