It is narrated from Sayyiduna 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 remain upon the fitrah (natural way) as long as they pray Maghrib before the stars appear."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6641