Mentions of Al-Jaleel:

From Quran And Hadies (Hadith)

Arabic Root:
From the root jim-lam-lam (ج ل ل), which has the following classical Arabic connotations: to be supremely great. To be glorious, majestic. To be sublime, to be high, lofty, far above, independent. The word Jalal (جلال) comes from the same root meaning greatness, majestic, and loftiness.

Among the disputed names:
As we've mentioned in previous names, different scholars have different criteria for what qualifies as a name of Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ. Of the 99 names, 81 are explicitly mentioned in the Qur'an. Therefore, there is not one agreed-upon list for the remaining 18 names. Al-Jalil is one of those names which is not included by certain scholars. This list includes Ibn al-Wazir, Ibn Hajar, and Ibn al-Uthaymeen. However, others, such as Ibn Arabi, Imam al-Bayhaqi, and Imam al-Ghazali, have included this name in their books of explanations of Asma ul-Husna. But many verses do describe this quality of Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ as being Al-Jalil.

وَيَبْقَىٰ وَجْهُ رَبِّكَ ذُو ٱلْجَلَـٰلِ وَٱلْإِكْرَامِ

Wa yabqaa wajhu rabbika zul jalaali wal ikraam

English Translation:
"And there will remain the Face of your Lord, Owner of Majesty and Honor."— (Qur'an 55:27)

What does it mean to be majestic?
The All-Majestic is an attribute only Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ can attain. What does it mean to be absolutely majestic? It means you have complete knowledge, strength, sovereignty, wealth, power, and dominion, among all the other attributes. His majesty is unique and immeasurable. It bears no resemblance to anything past, present, or future. There are many names which denote Allah's سُبْحَٰنَهُۥ وَتَعَٰلَىٰ greatness. For example, Al-Jalil is 'The Majestic' because of the perfection of all His attributes/qualities. Al-Kabir (the great), whose very essence is to be perfect. Al-Azeem (the magnificent one) - the one described as tremendous because of His attributes. All the attributes which mention the greatness, majesty or transcendent nature of Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ are called attributes of Jalal (majesty). The other attributes (i.e., mercy, kindness, care, provision, sustenance) are attributes of beauty (Jamal). It is said by scholars all of His names are either attributes of Jalal or Jamal. They are also interrelated, the majesty of Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ is His beauty, and His beauty is His majesty.

When Allah revealed Himself to Musa (as):

وَلَمَّا جَآءَ مُوسَىٰ لِمِيقَـٰتِنَا وَكَلَّمَهُۥ رَبُّهُۥ قَالَ رَبِّ أَرِنِىٓ أَنظُرْ إِلَيْكَ ۚ قَالَ لَن تَرَىٰنِى وَلَـٰكِنِ ٱنظُرْ إِلَى ٱلْجَبَلِ فَإِنِ ٱسْتَقَرَّ مَكَانَهُۥ فَسَوْفَ تَرَىٰنِى ۚ فَلَمَّا تَجَلَّىٰ رَبُّهُۥ لِلْجَبَلِ جَعَلَهُۥ دَكًّۭا وَخَرَّ مُوسَىٰ صَعِقًۭا ۚ فَلَمَّآ أَفَاقَ قَالَ سُبْحَـٰنَكَ تُبْتُ إِلَيْكَ وَأَنَا۠ أَوَّلُ ٱلْمُؤْمِنِينَ

Wa lammaa jaaa’a Moosa limeeqaatinaa wa kallamahoo Rabbuhoo qaala Rabbi arineee anzur ilaik; qaala lan taraanee wa laakininzur ilal jabali fa inistaqarra makaanahoo fasawfa taraanee; falammaa tajallaa Rabbuhoo liljabali ja’alahoo dakkanw wa kharra Moosaa sa’iqaa; falammaaa afaaqa qaala Subhaanaka tubtu ilaika wa ana awwalul mu’mineen

English Translation:
"And when Moses arrived at Our appointed time and his Lord spoke to him, he said, 'My Lord, show me [Yourself] that I may look at You.' [Allah] said, 'You will not see Me, but look at the mountain; if it should remain in place, then you will see Me.' But when his Lord appeared to the mountain, He rendered it level, and Moses fell unconscious. And when he awoke, he said, “Exalted are You! I have repented to You, and I am the first of the believers.'"— (Qur'an 7:143)

This ayah explains how Musa (as) asked to see Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ. But Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ responded that no one could bear to see Him, warning Musa (as) of the danger. Instead, He made His presence to a nearby mountain. What followed was the decimation of that mountain. It was said the mountain was leveled or flattened, meaning it was transformed into a flat land or a small hill. In that split second, just being close to His presence, Musa (as) fainted.

Reflection:
The connection of this story with the name Al-Jalil is Allah's beauty and majesty can't be understood through sight. The way we metaphorically see Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ is through the study and understanding of the attributes that make Him "The All-Majestic." Imam al-Ghazali writes of Allah's attributes, "and that is beautiful comportment 'or' beautiful disposition' perceived by insight rather than by sight." The one who understands how the inner has been perfected and properly proportioned will gain much more understanding and satisfaction than the one who judges beauty just by sight.

In this hadith, we see where the attribute of Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ as being called al-Jaleel originates, Mu'adh ibn Jabal narrated that the Messenger of Allah ﷺ said: "Allah, the Mighty and Sublime, said: 'Those who love each other for the sake of My Majesty (جَلاَلِي) shall be upon podiums of light, and they will be admired by the Prophets and the martyrs.'" ^[1]

This also covers the important topic of loving for the sake of Allah سُبْحَٰنَهُۥ وَتَعَٰلَىٰ. It's a message that encourages us never to stop searching for the good in humanity. To love your fellow person unconditionally because that's what Allah loves and will reward us for doing. Abu Huraira reported Allah's Messenger ﷺ as saying: Verily. Allah would say on the Day of Resurrection: Where are those who have a mutual love for My Glory's sake? Today I shall shelter them in My shadow when there is no other shadow but the shadow of Mine. ^[2]

The believer further benefits from knowing and understanding Al-Jalil by trying to perfect his interior attributes. Doing so will bring more beauty and pleasure into this world than any superficial looks could bring. As Imam Ghazali writes, "exterior beauty is of lesser worth."

References:
[1] Sahih (Darussalam) Jami` at-Tirmidhi 2390
[2] Sahih Muslim 2566