Mishkat al-Masabih 2144
He reported God's Messenger as saying:
“If anyone recites in the morning Hā Mīm al-Mu’min (Al-Qur’ān, 40:1-3) to ‘to Him is the final goal’ and the Throne Verse (Al-Qur’ān, 2:255) he will be guarded by them till the evening, and if anyone recites them in the evening he will be guarded by them till the morning.” 

Tirmidhī and Dārimī transmitted it, Tirmidhī saying this is a gharīb tradition.
وَعَنْ أَبِي هُرَيْرَةَ رَضِيَ اللَّهُ عَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: مَنْ قَرَأَ (حم)
الْمُؤْمِنَ إِلَى (إِلَيْهِ الْمَصِيرُ)
وَآيَةَ الْكُرْسِيِّ حِينَ يُصْبِحُ حُفِظَ بِهِمَا حَتَّى يُمْسِيَ. وَمَنْ قَرَأَ بِهِمَا حِينَ يُمْسِي حُفِظَ بهما حَتَّى يصبح ". رَوَاهُ التِّرْمِذِيّ والدرامي وَقَالَ التِّرْمِذِيّ هَذَا حَدِيث غَرِيب