The main purpose of this supplication is a way for a believer to testify the greatness of Allah, to praise him, to worship him.
In Sunan Abi Dawud Hadith 19, it mentions that the apostle of Allah used to remember Allah at all moments.
It is through Allah’s will that things happen. Abu Hurairah reported in Al-Bukhari and in Muslim that Allah is with those who are with him.
The Messenger of Allah (ﷺ) said, “Allah the Exalted says: ‘I am as my slave expects me to be, and I am with him when he remembers Me. If he remembers Me inwardly, I will remember him inwardly, and if he remembers Me in an assembly, I will remember him in a better assembly (i.e., in the assembly of angels).”
This sentiment is repeated in Surah Baqarah, ayat 152-153:
“So remember Me; I will remember you. And be grateful to Me and do not deny Me. O you who have believed, seek help through patience and prayer. Indeed, Allah is with the patient.”
The third kalima (also referred to as kalima tamjeed) is a perfect way to exalt Allah and remember him. Dhikr consists of two main ideas, the conscious effort required to move your tongue and the second is the niyyah or it’s effect in your heart.
Yes, remembering Allah will be rewarded as hadith 2910 Jami Tirmidhi “[Whoever recites a letter] from Allah’s Book, then he receives the reward from it, and the reward of ten the like of it.”
سُبْحَان اللهِ وَالْحَمْدُلِلّهِ وَلا إِلهَ إِلّااللّهُ وَاللّهُ أكْبَرُ وَلا حَوْلَ وَلاَ قُوَّةَ إِلَّا بِاللّهِ الْعَلِيِّ الْعَظِيْم
Transliteration: subhanallah walhamdulillah wala ilaha illallah wallahu akbar wala hawla wala quwwata illa billah aliyyil azeem
THE ENGLISH TRANSLATION OF KALIMA TAMJEED
The English translation of the third kalima is,
“Glory be to Allah and all praise be to Allah, there is none worthy of worship except Allah, and Allah is the Greatest. There is no might or power except from Allah, the Exalted, the Great One.“