Hadith Q339

وَإِعْلَامِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أُمَّتَهُ أَنَّهُمْ لَا يَزَالُونَ بِخَيْرٍ ثَابِتِينَ عَلَى الْفِطْرَةِ، مَا لَمْ يُؤَخِّرُوهَا إِلَى اشْتِبَاكِ النُّجُومِ‏.‏
And the Prophet (peace be upon him) informing his Ummah that they will always remain upon goodness and virtue; they will remain firm upon the natural disposition as long as they do not delay the Maghrib prayer until the stars are densely gathered.
Hadith Reference صحيح ابن خزيمه / كتاب‏:‏ الصلاة / Q339