A Commentary on the Treatise: The Excellence of al-Islam:

Islām is the surrender to Allāh, the Exalted, through Tawḥīd (His divine right to be worshipped alone) inwardly, and submission to Him outwardly through obedience, along with disavowal from shirk (associating partners with Him) and its people. It consists of three matters: submission to Allāh internally (i.e., sincerity of the heart to Allāh alone, such that one is humbled, obedient, and devoted in monotheism); outward submission (i.e., the limbs obey and comply with His commands); and disa...