"Al-Arba'in fi Usoul al-Din"

"Al-Arba'in fi Usoul al-Din" by Imam Al-Ghazali, also known as "The Forty Principles of Religion," is the essence of Quranic sciences as it brings together the foundations, pillars, and bases of religion. It is divided into four sections:

1. The first section deals with the fundamental principles of faith upon which religion rests, thus constituting the initial step in understanding religion and the starting point of faith.

2. The second section addresses outward actions and acts of worship.

3. The third section deals with the purification of hearts from sins and negative traits, thereby preparing hearts to receive divine light and spiritual knowledge.

4. The fourth and final section focuses on rectifying souls by adopting good values and guiding people towards the gates of happiness.

This book is, therefore, an essential collection that encompasses the principles of Islamic faith, acts of worship, the purification of souls, and the improvement of character to attain the path of happiness.