The first pillar of imaan (faith) in Islam is Belief in Allah. As Muslims, we believe in Allah in accordance with His beautiful names and attributes.
Allah has revealed His names repeatedly in the Quran primarily for us to understand who He is. Learning and memorizing the names of Allah will help us to identify the correct way to believe in Him. There is nothing more sacred and blessed than understanding the names of Allah and living by them. How do we expect to worship, love, fear and trust our Lord, The Almighty Allah, if we don’t know who He is?
Allah says in the Quran:
اَللّٰهُ لَاۤ اِلٰهَ اِلَّا هُوَ ؕ لَـهُ الۡاَسۡمَآءُ الۡحُسۡنٰى
Allah - there is no god but He. His are the most excellent names (that is, He possesses all the excellent attributes and characteristics) (Surah 20:8)
وَلِلَّهِ ٱلْأَسْمَآءُ ٱلْحُسْنَىٰ فَٱدْعُوهُ بِهَا ۖ وَذَرُوا۟ ٱلَّذِينَ يُلْحِدُونَ فِىٓ أَسْمَٰٓئِهِۦ ۚ سَيُجْزَوْنَ مَا كَانُوا۟ يَعْمَلُونَ
And to Allah belong the best 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 (Surah 7:180)
هُوَ اللّٰهُ الۡخَـالِـقُ الۡبَارِئُ الۡمُصَوِّرُ لَـهُ الۡاَسۡمَآءُ الۡحُسۡنٰىؕ يُسَبِّحُ لَهٗ مَا فِى السَّمٰوٰتِ وَالۡاَرۡضِۚ وَهُوَ الۡعَزِيۡزُ الۡحَكِيۡمُ
He is Allah, the Planner, Executer and Fashioner of creation. His are the names most beautiful. Whatever is in the heavens and the earth extols His Glory. He is the Most Mighty, the Most Wise (Surah 59:24)
Narrated Abu Huraira: Allah has ninety-nine Names, i.e., one hundred minus one, and whoever believes in their meanings and acts accordingly, will enter Paradise; and Allah is witr (one) and loves 'the witr' (i.e., odd numbers).
حَدَّثَنَا عَلِيُّ بْنُ عَبْدِ اللَّهِ، حَدَّثَنَا سُفْيَانُ، قَالَ حَفِظْنَاهُ مِنْ أَبِي الزِّنَادِ عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، رِوَايَةً قَالَ " لِلَّهِ تِسْعَةٌ وَتِسْعُونَ اسْمًا، مِائَةٌ إِلاَّ وَاحِدًا، لاَ يَحْفَظُهَا أَحَدٌ إِلاَّ دَخَلَ الْجَنَّةَ، وَهْوَ وَتْرٌ يُحِبُّ الْوَتْرَ ".
Reference: Sahih al-Bukhari 6410; Book 80, Hadith 105; Vol. 8, Book 75, Hadith 419
There are three levels of Enumerating the 99 names of Allah:
1) To count and know them and their expressions
2) To understand their meanings and that which they indicate.
For example, knowing that Allah is Al-Hakeem (the Wise) entails that the Muslim assigns all his affairs to Allah, since it is all according to His wisdom. Similarly, knowing that Allah is Al-Quddoos (the Holy) entails that the Muslim believes that free from all imperfections.
3) To call on Allah by them, and that is of two types:
a) Glorifying and worshiping Allah in accordance to these names
b) supplicating to Allah and asking Him by them.
The names of Allah and His Attributes both share the trait that it is allowed to seek refuge and to swear oaths by them, but there are some important differences between them, some of which are as follows:
A. It is allowed to supplicate to Allah using one of Us Names, or name oneself "the slave of" one of His Names, but this is not allowed with his Attributes. Thus, one may call himself Abd al-Kareem (the slave of the Most Generous) but not Abd al-Karam (slave of Generosity), and one may supplicate "O Most Generous (Kareem)!" but not "O Karam (Generosity) of Allah!"
B. One may derive Attributes from Allah's Names, but one may not derive names from his Attributes. Thus one may derive the Attribute 'rahmah' (mercy) from His Name 'Ar- Rahman' (The Merciful), but not the name 'al-mustawi' (The One who Rises Over) from His Attribute of 'al-istiwaa' (Rising Over)'.
C. One may not derive Names from the actions of Allah. Thus, one may not say that one of the names of Allah is al-ghaadib (the Angry) based on the fact that Allah becomes angry. One may, however, derive Attributes from His actions, and thus affirm that one of the Attributes of Allah is Ghadab (anger) due to the fact that He becomes angry.
Rest Allah alone knows best.
Source: Quran, Hadith, In the shade of Quran, An Explanation of the Last Tenth of the Noble Qur'an [Also with Critical Matters in the Life of a Muslim] Paperback – 2007; www.tafseer.info