This document is an introduction to the study of Tawheed (monotheism) in Islam by Ustaz Zhulkeflee Hj Ismail. It contains important dhikr (remembrances of Allah), dua (supplications), commands from the Quran and hadiths of the Prophet Muhammad. The key messages are the importance of having sure knowledge before making claims, avoiding hasty judgments, and distinguishing true Islamic beliefs and practices from those that associate partners with Allah (shirk). Outward similarities between religions are not the criteria—what matters most is one's beliefs regarding Allah's divinity and lordship alone.