"Four Key Concepts of the Quran" by Sayyid Abul A'la Mawdudi is a significant work that delves into four fundamental concepts that are central to the Quranic worldview. These concepts are:

1. **Risalah (Prophethood)**: The concept of prophethood in Islam, which involves the sending of messengers by God to guide humanity.

2. **Tawhid (Oneness of God)**: The central concept of monotheism in Islam, emphasizing the belief in the absolute unity and uniqueness of God.

3. **'Ibadah (Worship)**: The concept of worship in Islam, encompassing all acts of devotion and obedience to God.

4. **Akhirah (Hereafter)**: The belief in the afterlife, including resurrection, judgment, and eternal life, which is a key aspect of Islamic faith.

Mawdudi explores these concepts in depth, providing insights into their theological, philosophical, and practical dimensions as understood within the Quranic framework. The book aims to elucidate these foundational principles and their implications for individual believers and society at large, drawing upon Quranic verses and Islamic teachings to support its arguments. It serves as a valuable resource for those seeking a deeper understanding of core Islamic beliefs and their significance in shaping Muslim thought and practice.