Allah ﷻ said: "Has the time not come for those who have believed that their hearts should become humbly submissive at the remembrance of Allah and what has come down of the truth? And let them not be like those who were given the Scripture before, and a long period passed over them, so their hearts hardened." [Hadid 57:16].

And He ﷻ said: "Then We sent after them Our messengers, and We followed up [them] with Jesus, the son of Mary, and gave him the Gospel and We placed in the hearts of those who followed him compassion and mercy and monasticism, which they innovated; We did not prescribe it for them except [that they did so seeking] the approval of Allah. But they did not observe it with due observance." [Hadid 57:27].

And He ﷻ said: "And do not be like she who untwisted her spun thread after it was strong into untwisted strands." [Nahl: 92].

And He ﷻ said: "And worship your Lord until there comes to you the certainty (death)." [Hijr: 99].

And among the ahadith are:

قَالَ الله تَعَالَى: ﴿أَلَمْ يَأْنِ لِلَّذِينَ آمَنُوا أَنْ تَخْشَعَ قُلُوبُهُمْ لِذِكْرِ اللهِ وَمَا نَزَلَ مِنَ الْحَقِّ وَلا يَكُونُوا كَالَّذِينَ أُوتُوا الْكِتَابَ مِنْ قَبْلُ فَطَالَ عَلَيْهِمُ الأَمَدُ فَقَسَتْ قُلُوبُهُمْ﴾ [الحديد: ١٦]،

وَقالَ تَعَالَى: ﴿وَقَفَّيْنَا بِعِيسَى ابْنِ مَرْيَمَ وَآتَيْنَاهُ الأِنْجِيلَ وَجَعَلْنَا فِي قُلُوبِ الَّذِينَ اتَّبَعُوهُ رَأْفَةً وَرَحْمَةً وَرَهْبَانِيَّةً ابْتَدَعُوهَا مَا كَتَبْنَاهَا عَلَيْهِمْ إِلاَّ ابْتِغَاءَ رِضْوَانِ اللهِ فَمَا رَعَوْهَا حَقَّ رِعَايَتِهَا﴾ [الحديد: ٢٧]،

وَقالَ تَعَالَى: ﴿وَلا تَكُونُوا كَالَّتِي نَقَضَتْ غَزْلَهَا مِنْ بَعْدِ قُوَّةٍ أَنْكَاثًا﴾ [النحل: ٩٢]، 

وَقالَ تَعَالَى: ﴿وَاعْبُدْ رَبَّكَ حَتَّى يَأْتِيَكَ الْيَقِينُ﴾ [الحجر: ٩٩].

وَأَمَّا الأَحاديث فمنها: