Basics- What is Islaam? [Revisiting and Revising Basics]
In The Name of Allaah, The Most Merciful, The Bestower of Mercy.
What is Islaam? It is to submit to Allaah by worshipping Him alone. Therefore, whoever refuses to submit to Allaah is haughty, and whoever submits to Allaah and others [by devoting any act worship to Allaah and others], then he is guilty of being one who ascribes a partner to Allaah. So, through this it is known that Islam opposes two affairs: Haughtiness and Polytheism [or ascribing partners with Allaah in worship].
[Source: Explanation of Important Lessons For The Muslim Ummah. pages 41-42. Maktabah Malik Al-Fahad 1436AH. (2015)]