The Greatest of What Allāh Commanded With - Imām Ibn ‘Uthaymīn
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Shaykh Muḥammad b. Ṣāliḥ al-ʿUthaymīn - رحمه الله:
Tawḥīd is the greatest of what Allāh commanded with, because it is the foundation upon which the whole religion is built. And due to this, the Prophet started with it in the call to Allāh and commanded those he sent in Da’wah to start with it.
Sharḥ Uṣūl Ath-Thalāthah p.21
Translated by AMMAN CIRCLE Editorials