About the importance of the Quran
Nahj al-Balāgha|Volume 1|Book 1|Chapter 183
وَاعْلَمُوا أَنَّهُ لَنْ يَرْضَى عَنْكُمْ بِشَيء سَخِطَهُ عَلَى مَنْ كَانَ قَبْلَكُم، وَلَنْ يَسْخَطَ عَلَيْكُمْ بِشَىْء رَضِيَهُ مِمَّنْ كَانَ قَبْلَكُمْ، وَإِنَّمَا تَسِيرُونَ فِي أَثَر بَيِّن، وَتَتَكَلَّمُونَ بِرَجْعِ قَول قَدْ قَالَهُ الرِّجَالُ مِنْ قَبْلِكُمْ، قَدْ كَفَاكُمْ مَؤُونَةَ دُنْيَاكُمْ، وَحَثَّكُمْ عَلَى الشُّكْرِ، وَافْتَرَضَ مِنْ أَلْسِنَتِكُمُ الذِّكْرَ.
You should know that He will not be pleased with you for anything for which He was displeased with those before you, and He will not be displeased with you for anything for which He was pleased with those before you. You are treading on a clear path, and are speaking the same as the people before you had spoken. Allāh is enough for your needs in this world. He has persuaded you to remain thankful, and has made it obligatory on you to mention Him with your tongues.