By Shaykh Saalih ibn ‘Abdillaah Al-Fawzaan (hafidhahullaah)
In the Name of Allaah, the Lord of all the worlds, may His Most Complete Salaah and Salaam be upon His final Prophet and Messenger, and upon all his family members and companions, to proceed:
We have previously stated that the three categories of tawheed are taken directly from the Noble Qur’aan. The categories are taken from many verses, so let us look to some of them now.
The very first chapter found in the mus-haf, Soorah Al-Faatihah, mentions all three categories of tawheed. Allaah says :
“All the praise is due to Allaah, the Lord of all that exists”
Here is tawheed ar-ruboobiyyah, as the verse establishes Allaah’s Lordship over the ‘aalameen, which means everything except Allaah, and the Rabb (Lord) means the Owner and Controller of Affairs. Allaah then says :
“The Bestower of Mercy, the All-Merciful, the Owner of the Day of Judgement”
Tawheed al-asmaa’ was-sifaat is present in these verses, as Allaah establishes for Himself the attributes of Mercy and Ownership. He also establishes some of His Names - Ar-Rahmaan, Ar-Raheem, and Al-Maalik. Then He says 
“You alone we worship, and You alone we seek help from”
And here is tawheed al-uloohiyyah, as the verse demonstrates the obligation to single out Allaah with acts of worship, and to seek help from Him alone.
Similarly, the three categories of tawheed are also found in Soorah An-Naas, the very last chapter to be found in the mus-haf. Tawheed ar-ruboobiyyah is found in His Statement :
“Say: ‘I seek refuge in the Lord of mankind’”
And tawheed al-asmaa’ was-sifaat is found in His Statement :
“the King of mankind”
And lastly, tawheed al-uloohiyyah is found in His Statement :
“the God worshipped by mankind”
Likewise, the very first command issued in the mus-haf contains the categories of tawheed :
“O mankind! Worship your Lord who created you and those who came before you, so that you might attain taqwaa. (He is) the One who made the earth a bed for you and the sky a mighty structure, and He sent water down from the sky that brings forth many fruits for your provisions. So do not ascribe partners to Allaah while you have knowledge!”
After mentioning the three kinds of people, the believers, the disbelievers, and the hypocrites, and then turning His Servants to the Qur’aan as a source of guidance , He followed that up saying :
“O mankind! Worship your Lord!”
This is a general call, a command to the entire creation, to single out Allaah with acts of worship, and a command to avoid ascribing a single partner to Allaah. This is tawheed al-uloohiyyah.
Then Allaah comes with tawheed ar-ruboobiyyah, as something to back up the fact that He deserves to be worshipped alone :
“The One who made the earth a bed for you and the sky a mighty structure, and He sent water down from the sky that brings forth many fruits for your provisions”