There is no god worthy of worship except Allah in truth and Muhammed (peace and blessings of Allah be upon him) is his messenger. This testimony of faith incorporates pure monotheism.
Source: https://torontodawah.com/pdf-this-is-islam-shaykh-abdul-aziz-ibn-abdullah-al-shaykh/
Author: Shaykh Abdul-Aziz Ibn Abdullah Al-Shaykh
From the Book: Good Morals towards one’s Lord: A Muslim must observe the highest forms of morals towards his Lord in whatever is related to his soul. Love for Him, fear of Him, invoking him alone, humbling oneself before Him, relying on Him and having a high opinion of Him are some of the great obligatory morals that man must observe towards his Lord. His good morals towards his Lord also include being sincere to him in religion and not intending any act of worship except for Him alone.
SalafiMakthaba Quran and Sunnah according to the understanding of the righteous predecessors.