Fataawa Arkanul Islaam
Shaykh Muhammad Uthaymeen {Rahimahullah}
Vol. 1 pgs. 78-79

Question:How does the testimony La Ilaha illallah (None has the right to be worshipped except Allah) include all types of Tawheed?

Answer:
It includes all types of Tawhid either by implication or as a requirement. This is because when a person says: I testify that none is worthy of worship except Allah, it comes immediately to mind that what is intended by it is affirming Allah's sole right to be worshipped, which is known as Tawhid Al-Uloohiyah and this implies Tawhid Ar-Rububiyyah, because every person who worships Allah Alone would not do so unless he acknowledged His o*neness in matters of Lordship. Likewise, it implies Tawhid Al-Asmaa was-Sifaat, because a person does not worship except o*ne Whom he knows has the right to be worshipped because of the Names and Attributes which belong to Him. Ibraheem (alayhee salaam) said to his father:

"O my father! Why do you worship that which hears not, sees not and cannot avail you in anything?" {Surah Maryam 19:42}

So affirming Allah's sole right to be worshipped implies Tawhid Ar-Rububiyyah and Tawhid Al-Asma' was-Sifaat.