It is narrated from Sayyiduna Abu Ayyub al-Ansari (may Allah be pleased with him); he said: I heard the Messenger of Allah (peace and blessings be upon him) say: "My Ummah will remain upon good, or upon the fitrah (natural way), as long as they do not delay the Maghrib prayer until the stars become crowded together."
Hadith Referenceالمعجم الكبير للطبراني / باب الخاء / 4068