1) God's Oneness as Creator - that only God creates. He is the Only one to be worshipped. Anything else you worship ( or obey ) is a false god.
2) God's Oneness as Lord - that only God determines and controls. He is the Only One who will give you success or failure - so do not be afraid of anything else.
3) God's Oneness in His attributes - that the attributes of God are unique to Him alone. For example - He is the only true source of Mercy, the only true source of Peace, the only true King, the only true Judge, etc.
Once these three have been understood and applied then,and only then, will a person be living by true "Tawheed".
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