The tawheed of Allah in His names requires the belief in each and every name He ascribed to Himself; and belief in the qualities and consequences incorporated in them. Take for example Ar-Rahmaan 'the Merciful' which was mentioned in the Qur’aan on more than one occasion. We must believe in it as one of the names of Allah, believe in the fact that mercy is one of the attributes of Allah, and also believe that Allah has mercy upon whomever He wishes. The same applies to all the other names of Allah mentioned in the Qur'aan or in the Sunnah of His Prophet (sallallahu ‘alaihi wa sallam).

The names of Allah are those proper nouns employed in reference to Him in the Qur’aan and the Sunnah. Every one of those names refers to one or more attributes of Allah. Each name is derived from its verbal noun, such as the All-Knowing (Al-‘Aleem), the Able (Al-Qaadir), the All-Hearing (As-Samee’), the All-Seeing (Al-Baseer), and so on. The name Al-‘Aleem (the All-Knowing), for example, is derived from the attribute of 'knowledge', and the same is true of the Merciful (Ar-Rahmaan), etc.

The name that incorporates the meanings of all the other nouns and attributes is the name 'Allah'. Some scholars, such as Ibnul-Qayyim, Sibawayh and At-Tabari, contended that it is derived from the word 'Al-Ilaah', meaning the God. Others maintained that it is not derived from any other word. There is no contradiction between those names being adjectives or nouns. The name 'Merciful' (Ar-Rahmaan), for instance, is both a proper noun and an adjective. All of Allah's names are adjectives of praise as well as being references to their proper meanings. Those names were described as beautiful (husnaa in Arabic) because they describe the Most Excellent and Exalted Creator.

The Number Of Allah's Names
"Rules Of Thumb" For Understanding Allah's Names
Evidence For The Tawheed Of Names & Attributes
The Rules & Conditions Which Determine The Names & Attributes Of Allah
Two Major Classifications Of Deviated Groups On This Issue
Description Of 99 Names & Attributes Of Allah