Sahih Muslim 2755
'Ala' reported on the authority of his father who reported on the authority of Abu Huraira that Allah's Messenger (ﷺ) said:
If a believer were to know the punishment (in Hell) none would have the audacity to aspire for Paradise (but he would earnestly desire to be rescued from Hell), and if a non-believer were to know what is there with Allah as a mercy. none would have been disappointed in regard to Paradise.
حَدَّثَنَا يَحْيَى بْنُ أَيُّوبَ، وَقُتَيْبَةُ، وَابْنُ، حُجْرٍ جَمِيعًا عَنْ إِسْمَاعِيلَ بْنِ جَعْفَرٍ، قَالَ
 ابْنُ أَيُّوبَ حَدَّثَنَا إِسْمَاعِيلُ، أَخْبَرَنِي الْعَلاَءُ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى
 الله عليه وسلم قَالَ ‏
"‏ لَوْ يَعْلَمُ الْمُؤْمِنُ مَا عِنْدَ اللَّهِ مِنَ الْعُقُوبَةِ مَا طَمِعَ بِجَنَّتِهِ أَحَدٌ وَلَوْ
 يَعْلَمُ الْكَافِرُ مَا عِنْدَ اللَّهِ مِنَ الرَّحْمَةِ مَا قَنِطَ مِنْ جَنَّتِهِ أَحَدٌ ‏"‏ ‏.‏