In The Name of Allaah, The Most Merciful, The Bestower of Mercy
Allaah [The Most High] said:
أَلَمْ يَأْنِ لِلَّذِينَ آمَنُوا أَن تَخْشَعَ قُلُوبُهُمْ لِذِكْرِ اللَّهِ وَمَا نَزَلَ مِنَ الْحَقِّ وَلَا يَكُونُوا كَالَّذِينَ أُوتُوا الْكِتَابَ مِن قَبْلُ فَطَالَ عَلَيْهِمُ الْأَمَدُ فَقَسَتْ قُلُوبُهُمْ ۖ وَكَثِيرٌ مِّنْهُمْ فَاسِقُونَ
Has not the time come for the hearts of those who believe [in the Oneness of Allah – Islamic Monotheism] to be affected by Allah’s Reminder [this Qur’an], and that which has been revealed of the truth, lest they become as those who received the Scripture [the Taura (Torah) and the Injeel (Gospel)] before, and the term was prolonged for them and so their hearts were hardened? And many of them were Fasiqun [rebellious, disobedient to Allah].
[Soorah Al-Hadeed: Ayah: 16]
Imaam Ibnul Qayyim [rahimahullaah] said:
And when it is the case that Eemaan necessitates humility and calls for it, therefore they were called [to move up] from the station of Imaan to the station of Ihsaan; Meaning, ‘’Has the time not come for them to reach Ihsaan through Imaan and actualize that through their submission to Allaah’s Reminder [The Qur’aan], which Allaah sent down to them. Ibn Mas’ood [radiyallaahu-anhu] said, ‘’There was only four years between our [embracing] Islaam and [the revelation of this] admonition to us. [Ref 1]
And regarding the statement of Allaah:
وَلَا يَكُونُوا كَالَّذِينَ أُوتُوا الْكِتَابَ مِن قَبْلُ فَطَالَ عَلَيْهِمُ الْأَمَدُ فَقَسَتْ قُلُوبُهُمْ ۖ وَكَثِيرٌ مِّنْهُمْ فَاسِقُونَ
Lest they become as those who received the Scripture [the Taurat (Torah) and the Injeel (Gospel)] before, and the term was prolonged for them and so their hearts were hardened?’’
Imaam as-Saa’di [rahimahullaah] said:
That is: Do not become like those to whom Allaah revealed the book, which obligates humility and complete submission on the hearts; but they [i.e. those who received the scripture] neither preserved [the scripture] nor were they firm [in holding unto it]; rather the term was prolonged for them whilst they continued upon heedlessness, so their Eemaan dwindled and their certainty ceased. So, the hearts are always in need of a reminder regarding that which Allaah has revealed and the wisdom behind it. It is not permissible to be heedless of that, for indeed that is a cause for the hardening of the hearts. [Ref 2]
[Ref 1: Source: Badaa’i At-Tafseer Al-Jaami Limaa Fassarahu Al-Imaam Ibnul Qayyim’ page 129. Vol 3. Publisher: Daar Ibn Al-Jawziyyah 2nd ed 1431AH. Abridged & slightly paraphrased]
[Ref 2: Source: Tayseer Al-Kareem Ar-Rahmaan fee Tafseer Kalaam al-Mannaan’. Publisher: Daar Ibn Hazm 1st ed 1424AH (Year 2003). Abridged & slightly paraphrased]