They are not the Most Beautiful Names just because of the words themselves, but because they indicate His most Perfect Attributes. All Allah&"s Names are praiseworthy, laudable, meritable and deserve to be glorified, and that is the reason why they are the Most Beautiful Names. His Attributes are the Most Perfect, all His Descriptions are the Most Glorified, and all His Actions are carried out in complete wisdom, mercy, and justice.
A part of Iman is to believe in the Names and Attributes of Allah (mighty and majestic is He) as they are mentioned in His Book and in the authenticated Sunnah of His Prophet (peace be upon him), and Iman in His Names and Attributes is dependent on two principles:
The First Principle:
Affirming Allah&"s Names and Attributes in a manner appropriate to his glory without tahreef (changing/distorting any of them to other than their true meaning), ta’teel (denying some or all of them), takeef (questioning “how” Allah’s Name or Attribute is performed, i.e. how He descends to the lower heavens, etc.), tamtheel (to claim there is a resemblance between Allah’s Names and Attributes and those of His creation). Allah says: &"There is nothing like unto Him, and He is the Hearing, the Seeing&" (Ash-Shûra: 11).
The Second Principle:
To understand their meanings and to affirm the attributes which the Names stand for without trying to know how these attributes are actually carried out. Allah says: &"Allah knows what is (presently) before them and what will be after them, but they do not encompass it in knowledge&" (Tâ-Hâ: 110).
Allah (peace be upon him) explained the reason He informed His slaves of His Supreme Names and Attributes, and this is to worship Him by using them. Allah the Exalted says: &"Say, &"Call upon Allah or call upon the Most Merciful. Whichever (name) you call - to Him belong the Most Beautiful Names&" &" (Al-Isrâ&": 110).
Allah (mighty and majestic is He) says: &"To Allah belong the Most Beautiful Names, so invoke Him by them; and leave (the company of) those who practice deviation concerning His names. They will be recompensed for what they have been doing” (Al-A&"râf: 180).
This includes supplicating Allah (invoking Allah) using His Most Beautiful Names and Attributes, and this incorporates both kinds of supplications: supplication of need, such as when the slave says: &"O Merciful Allah, have mercy on me! O Beneficent Lord, grant me due to your beneficence!&" The other kind of supplication is that of praise and worship in which a person glorifies Allah using His Most Beautiful Names and Attributes without actually asking for anything. This praise could be carried out with the heart or the tongue.
It refers to those who belie or deny (or utter impious speech against) Allah’s (mighty and majestic is He) Names. This is to deny or belie any of His Names which are mentioned in His Book, or to liken His Attributes to any attributes of His creation, or to give Him a name or an attribute that does not befit His Majesty - those that have no evidence from the Words of Allah or the Sunnah of His Prophet (peace be upon him).