'Ala' reported on the authority of his father who reported on the authority of Abu Hurairah (RA) 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.
´Abu Hurairah narrated that the Messenger of Allah (ﷺ) said:` “If the believer knew what is with Allah of punishment, none would hope for Paradise, and if the disbeliever knew what is with Allah of mercy, none would despair of (attaining) Paradise.”
Shaykh Dr. Abdur Rahman Freywai
Explanation: 1: In the determination of these punishments, Allah has not acted unjustly towards anyone. They are entirely in accordance with justice. Allah is absolutely not unjust to His servants. As for the matter of the mercy of Paradise, that is a matter of ninety-nine out of a hundred.
Source: Sunan al-Tirmidhi – Majlis ‘Ilmi Dar al-Da‘wah, New Delhi Edition, Page: 3542