Jundub ibn Abdullah reported: The Messenger of Allah, peace and blessings be upon him, said, “Whoever performs the dawn prayer (fajr) will be under the protection of Allah, so beware lest Allah questions you about what you owe him. For if Allah questions anyone of you and he falls short of fulfilling the duty which he owes him, then He will retaliate for him and throw him upon his face into the Hellfire.”

Source: Sahih Muslim 657

Grade: Sahih (authentic) according to Muslim

جُنْدَبًا الْقَسْرِيَّ يَقُولُ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ مَنْ صَلَّى صَلَاةَ الصُّبْحِ فَهُوَ فِي ذِمَّةِ اللَّهِ فَلَا يَطْلُبَنَّكُمْ اللَّهُ مِنْ ذِمَّتِهِ بِشَيْءٍ فَإِنَّهُ مَنْ يَطْلُبْهُ مِنْ ذِمَّتِهِ بِشَيْءٍ يُدْرِكْهُ ثُمَّ يَكُبَّهُ عَلَى وَجْهِهِ فِي نَارِ جَهَنَّمَ

657 صحيح مسلم كِتَاب الْمَسَاجِدِ وَمَوَاضِعِ الصَّلَاة من صلى الصبح فهو في ذمة الله

http://dailyhadith.abuaminaelias.com/2013/05/02/hadith-on-prayer-whoever-prays-the-fajr-prayer-comes-under-the-protection-of-allah/