Assalamu alaikum

Bismillahi Wassalatu wassalamu 'ala rasulillah wa 'ala ali wasahbie ajama'in

All Praise Is Due to Allah (swt) the Lord of the Universe, the one, The Supreme , The High , The king of All kings All the best names is for Allah (swt) and Peace and salutation to our Prophet Muhammad (saw) and to his Family, companions and those who Believe in him until the last day.

The Disbelievers will someday wish that they had been Muslims.

Allah said:

How much would those who disbelieved wish, 

Here Allah tells us that they will regret having
lived in disbelief, and will wish that they had been
Muslims in this world.  


How much would those who disbelieved wish that they
had been Muslims.  


Sufyan Ath-Thawri reported from Salamah bin Kuhayl,
who reported from Abi Az-Za`ra', from Abdullah, who
said:  
"This is about the
Jahannamiyyun (the sinners
among the believers who will stay in Hell for some
time), when they (the disbelievers) see them
being brought out of Hell.''  


2 
Ibn Jarir reported that Ibn Abbas and Anas bin Malik
explained that;  
this
Ayah refers to the Day when Allah will detain
the sinful Muslims in Hell along with the idolators.  
He said:  
"The idolators will say to them, `What you used
to worship on earth has not helped you.'  


Then by virtue of His mercy, Allah will be angry
for their sake, and He will remove them (from it). 
That is when (How much would those who disbelieved wish that they had been Muslims).''  

Tafsir Ibn kathir 
Surah Hijr ayat 2