The Excellence of Tawheed and what it expiates of sins
فضل التوحيد وما يكفر من الذنوب
Allaah Ta’ala said
(ٱلَّذِینَ ءَامَنُوا۟ وَلَمۡ یَلۡبِسُوۤا۟ إِیمَـٰنَهُم بِظُلۡمٍ أُو۟لَـٰۤئكَ لَهُمُ ٱلۡأَمۡنُ وَهُم مُّهۡتَدُونَ)
It is those who believe (in the Oneness of Allah and worship none but Him Alone) and confuse not their belief with Zulm (wrong i.e. by worshipping others besides Allah), for them (only) there is security and they are the guided.
[Surah Al-An’am 82]