قُلْ هُوَ اللَّهُ أَحَدٌ

This verse succinctly declares the oneness of Allah, which is the foundation of Islamic belief. It refutes polytheism and emphasizes that Allah is unique, without partners or equals. The concept of Divine Unity (Tawhid) expressed here is central to Islamic theology and shapes a Muslim's worldview and actions. This simple yet profound statement forms the core of Islamic monotheism.