The Evidence of Tawhid (Surah Fatir 35: 3)

Allah shows His servants that they should worship Him Alone, for just as He is Independent in His power of creation and provision, so He should be worshipped Alone with no partners or associates such as idols and false gods. So Allah says:

La ilaha illa Huwa.  How then are you turning away (from Him)) meaning, `how can you turn away from Him after this has been made clear and this proof has been made obvious, but you still worship idols and false gods' And Allah knows best.

Source: Tafsir ibn Kathir (Abridged)