#3. Al-Qur'an

The Qur'an is a living guide for Muslims. When we want peace of mind then study the Qur'an. In the Hadith Rasulullah! explains "Read the Qur'an By you all, because the recitation of the Qur'an that is read when living in this world will be a syafa'at or a helper for its readers on the Day of Judgment later." (HR.Muslim). So it is advisable to read the Quran while still able to get Syafa'at on the Day of Judgment later.