Sahih Muslim 23 a
It Is narrated on the authority of Abu Malik: I heard the Messenger of Allah (ﷺ) say: He who professed that there is no god but Allah and made a denial of everything which the people worship beside Allah, his property and blood became inviolable, an their affairs rest with Allah.

• This hadith from Sahih Muslim 23 a conveys that a person who believes and professes that there is only one true God, Allah, and denies worshiping any other deity, their life and property becomes sacred and inviolable. This statement highlights the importance of belief in the oneness of Allah in Islam, which is the central tenet of the Islamic faith. The use of the word “god” refers to the concept of a deity or an object of worship, which is called “ilah” in Arabic. However, the use of “Allah” with a capital “God” refers to the unique and only true God in Islamic belief. Muslims believe that there is no other deity worthy of worship except Allah, who is the Creator of the universe and everything in it. while the word “ilah” can be used more broadly to refer to any deity or god, Muslims believe that there is no god or ilah except Allah. The hadith emphasizes that once a person has declared their faith in Allah and rejected all false deities, their life, property, and affairs are protected by Allah. This protection is a divine blessing and a reward for accepting the oneness of Allah and submitting to His will.