Is there any evidence on classifying Tawhid (belief in the Oneness of Allah/ monotheism) into three categories?
Classifying Tawhid into three categories is based on induction after scholars studied the relevant texts in the Qur'an and Sunnah. Some scholars added a fourth category calling it Tawhid of Mutaba`ah (following). All these categories are based on induction.
You (Alone) we worship, and You (Alone) we ask for help (for each and everything).
O mankind! Worship your Lord (Allâh), Who created you and those who were before you so that you may become AlMuttaqûn (the pious See V.2:2).
And your Ilâh (God) is One Ilâh (God Allâh), Lâ ilâha illa Huwa (there is none who has the right to be worshipped but He), the Most Gracious, the Most Merciful.
And I (Allâh) created not the jinn and mankind except that they should worship Me (Alone). I seek not any provision from them (i.e. provision for themselves or for My creatures) nor do I ask that they should feed Me (i.e. feed themselves or My creatures). Verily, Allâh is the AllProvider, Owner of Power, the Most Strong.
Say (O Muhammad ﺻﻠﻰ ﺍﷲ ﻋﻠﻴﻪ ﻭﺳﻠﻢ): "He is Allâh, (the) One. "AllâhusSamad (ﺍﻟﺴﻴﺪ ﺍﻟﺬﻱ ﻳﺼﻤﺪ ﺇﻟﻴﻪ ﻓﻲ ﺍﻟﺤﺎﺟﺎﺕ) [Allâh the SelfSufficient Master, Whom all creatures need, (He neither eats nor drinks)]. "He begets not, nor was He begotten. "And there is none coequal or comparable unto Him."
The right of Allah over His slaves is that they should worship Him and not associate anything with Him.
Whoever dies while still invoking a rival (in worship) to Allah, will enter Hell (Fire).
To worship Allah and never associate anything with Him, perform the obligatory Prayer, and pay the prescribed Zakah...
My entire Ummah will enter Paradise except those who refuse, then it was said: O' Messenger of Allah , who will refuse? He said, "Whoever obeys me will enter Paradise, and whoever disobeys me is the one who refuses"