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
The Qur'an is a healing for the hearts:
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 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.

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

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.

Explained in Detail/41:44 "Had We made it a Qur´an in a foreign language, they would have said, "Should not its verses have been explained?"Whether in a foreign language or in Arabic, say, "It is a guide and a cure for those who believe (regardless of their language). As for those who do not believe, their ears are heavy. It is closed to them as if it were addressed to them from a distant place."

Prophet Jonah/10:57 O people, there has come to you from your Lord a reminder, a healing for whatever troubles the hearts, a guidance and a mercy for those who believe.

The Night Journey/17:82 We have sent down the Qur´an as a healing and mercy for those who believe, while it only increases the harm of the wrongdoers.