The Pilgrimage - 22:35 They are such that their hearts tremble at the mention of Allah. They are patient in what befalls them, they observe the prayer and spend out of what We have provided them for charity.
When Allah is mentioned, the hearts of the believers tremble:
The Spoils of War/8:2 Those who believe are such that their hearts tremble when Allah is mentioned, and their faith increases when His verses are recited to them, and they trust in their Lord.

The Thunder/13:28 Those who believe and their hearts find peace in the remembrance of Allah. Know that the hearts are soothed by the remembrance of Allah.

The Companies/39:23 Allah has sent down the best hadith in a coherent book in two parts. The skins of those who honor their Lord tremble because of it. Then their skins and hearts soften towards the message of Allah. This is Allah´s guidance; He guides whom He wills and/or guides whom He wills to it. There is no guidance for anyone whom Allah leads astray