Sayyidunā ʾAbdullāh ibn Masʿūd رضي الله عنه narrated: “On one occasion, I went by the Noble Prophet ﷺ and he was suffering from an intensely high fever. I asked: ‘O Messenger of Allāh! You have a very intensely high fever.’
(In some narrations, it is also mentioned that he was suffering from such an intensely high fever that the heat of his fever could be felt from above the sheet which was covering the Noble Prophet ﷺ.)
So the Prophet ﷺ said: “I suffer from such high fever which is equivalent to the fever two men from among you.” (Meaning, the intensity of the fever which two people generally experience, I alone, suffer from such intense fever.)
This is the condition of Allāh Taʿālā’s special servants.
It is mentioned in the Pure Ḥadīth that the Noble Prophet ﷺ said: “The most severe tests, trials and hardships afflict the Prophets. Thereafter, (these difficult states prevail over) those who resemble them the most (in proportion to their resemblance).” [See: Jāmiʿ Tirmidhī #2398]
Thus, this is also the case with fever. The Prophet, ﷺ alone would suffer from fever which two men would generally suffer from. Upon this, Sayyidunā Ibn Masʿūd رضي الله عنه said: “I asked: ‘O Messenger of Allāh! Is this the matter so that you will also receive double the reward?’ The Prophet ﷺ replied: ‘Yes. Double the reward is also attained.’” Meaning, he receives more reward than others.Allāh expiates the sins of any Muslim who is afflicted by an injury, a thorn-prick or worse and his sins fall away as leaves fall from a tree (in autumn).” [Ṣaḥīḥ Bukhārī #5648]
[Dars Riyāḍuṣ Ṣāliḥīn Vol.1 Pg.296-297 by Hazrat Muftī Aḥmed Khānpūrī Ṣāḥib حفظه الله ونفعنا بعلومه وفيوضه وصحبته ]