The next section discusses “afflictions of love” – these are afflictions that occur to a person who when he or sheinvestigate their deeds finds no sin and investigates their commitment to Torah study and finds no failings – then “it can be assumed that they are ‘afflictions of love’ – as it is stated: For Hashem rebukes the one He loves. [Proverbs 3:12]
From Ramban (Nachmanides): “. . . out of love and compassion, God cleanses people from their inadvertent sins by afflicting them in this world. They are thus rendered fit to receive their full measure of reward in the World to Come.”
From Rashi: “God therefore shifts the onus of punishment from the average people onto the righteous, who will bear it with love. Since a righteous person who is afflicted for this reason is suffering on behalf of others, he is credited with the reward that is consequently taken from them.”
From Tzlach: “’The reward is in proportion to the exertion’ (Pirkei Avos 5:23). Thus, by visiting suffering upon the righteous, God increases their opportunities for reward.”
One of the sections on afflictions of love says:
Now, if the loss of a tooth or eye, which is only one of the limbs of a person, -- a slave goes free on account of it, then afflictions, which purge a person’s entire body, all the more so should a person be freed (i.e. from sin) on account of them!
The commentary states: “When a Canaanite slave goes free because his master injured one of his limbs he assumes the status of a free Jew. Thus, through the freedom wrought by his injury, he ascends from a lower level of sanctity to a higher level. This is, therefore, a fitting analogy to the suffering of a righteous person, which likewise frees him from his previous lower status and brings him close to the Almighty. He, too, is liberated in the sense that previously he was only God’s servant, but now he is God’s ‘child’ (Pnei Yehoshua)”