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 Taurat (Torah) and the Injeel (Gospel)] before (i.e. Jews and Christians), 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 Imaan necessitates humility and calls for it, therefore they were called 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 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 [the period when we accepted] 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 (i.e. Jews and Christians), and the term was prolonged for them and so their hearts were hardened?]: Imaam as-Saa’di (rahimahullaah) said: Meaning: Do not be like those to whom Allaah revealed the book, which obligates – on the hearts – humility and complete submission; but they neither preserved [the scripture] nor were they firm on it; rather the term was prolonged for them whilst they continued upon heedlessness, so their Imaan dwindled and their certainty ceased. Therefore, at all times the hearts are in need of a reminder of that which Allaah has revealed and speech about its wisdom. 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: An Excerpt from ‘Badaa’i At-Tafseer Al-Jaami Limaa Fassarahu Al-Imaam Ibnul Qayyim’ page 129. Vol 3. Publisher: Daar Ibn Al-Jawziyyah 2nd ed 1431AH. Slightly paraphrased]; [Ref 2: An Excerpt from ‘Tayseer Al-Kareem Ar-Rahmaan fee Tafseer Kalaam al-Mannaan’. Slightly paraphrased]