From Quran
ٱلَّذِينَ ءَامَنُواْ وَتَطۡمَئِنُّ قُلُوبُهُم بِذِكۡرِ ٱللَّهِۗ أَلَا بِذِكۡرِ ٱللَّهِ تَطۡمَئِنُّ ٱلۡقُلُوبُ
الرعد : ٢٨
Those who believe (in the Oneness of Allah – Islamic Monotheism), and whose hearts find rest in the remembrance of Allah, Verily, in the remembrance of Allah do hearts find rest.
Surah Ar-Ra`d: 28
Hadith: Arabic Text followed by English Translation.
عَنْ أَبِي هُرَيْرَةَ ـ رضى الله عنه ـ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ
مَنْ قَالَ سُبْحَانَ اللَّهِ وَبِحَمْدِهِ. فِي يَوْمٍ مِائَةَ مَرَّةٍ حُطَّتْ خَطَايَاهُ، وَإِنْ كَانَتْ مِثْلَ زَبَدِ الْبَحْرِ
رواه البخاري ٦٤٠٥
Narrated Abu Huraira: Allah’s Messenger (ﷺ) said,
Whoever says ‘Subhaan Allaahi wa bi hamdihi (Glory and praise be to Allaah)’ one hundred times in a day, his sins will be erased, even if they are like the foam of the sea.
Narrated by Al-Bukhari, 6405