وَعَنِ ابْنِ عُمَرَ رَضِيَ اللَّهُ عَنْهُمَا
قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «إِنَّ هَذِهِ الْقُلُوبَ تَصْدَأُ كَمَا يَصْدَأُ الْحَدِيدُ إِذَا أَصَابَهُ الْمَاءُ». قِيلَ: يَا رَسُولَ اللَّهِ وَمَا جِلَاؤُهَا؟ قَالَ: «كَثْرَةُ ذِكْرِ الْمَوْتِ وَتِلَاوَةِ الْقُرْآنِ»
Ibn Umar reported God’s messenger as saying, “These hearts become rusty just as iron does when water gets to it.” On being asked what could clear them he replied, “A great amount of remembrance of death and recitation of the Qur’an.” Transmitted by Baihaqi in Shuab al-iman.
Mishkat al-Masabih 2072, Book 9, The Excellent Qualities of the Qur'an, Hadith 58. 1 min read