“ R. Zera says: Come and see how the way of human beings differs from the way of the Holy One, blessed be He. It is the way of human beings that when a man sells a valuable object to his fellow, the seller grieves and the buyer rejoices. The Holy One, blessed be He, however, is different. He gave the Torah to Israel and rejoiced. For it is said: For I give you good doctrine; forsake ye not My teaching.”
“ Raba says: If a man sees that painful sufferings visit him, let him examine his conduct. For it is said: Let us search and try our ways, and return unto the Lord. If he examines and finds nothing [objectionable], let him attribute it to the neglect of the study of the Torah. For it is said: Happy is the man whom Thou chastise, O Lord, and teach out of your law. If he did attribute it [thus], and still did not find [this to be the cause], let him be sure that these are chastising of love. For it is said: For whom the Lord loves He corrects.”
“Raba, in the name of R. Sahorah, in the name of R. Huna, says: If the Holy One, blessed be He, is pleased with a man, he crushes him with painful sufferings. For it is said: And the Lord was pleased with [him, hence] he crushed him by disease. Now, you might think that this is so even if he did not accept them with love. Therefore it is said: To see if his soul would offer itself in restitution. Even as the trespass-offering must be brought by consent, so also the sufferings must be endured with consent. And if he did accept them, what is his reward? He will see his seed, prolong his days. And more than that, his knowledge [of the Torah] will endure with him. For it is said: The purpose of the Lord will prosper in his hand.”
R. Jacob b. Idi and R. Aha b. Hanina differ with regard to the following: The one says: chastisings of love are such as do not involve the intermission of study of the Torah. For it is said: Happy is the man whom Thou chastise, O Lord, and teach out of your law. And the other one says: chastisings of love are such as do not involve the intermission of prayer. For it is said: Blessed be God, Who has not turned away my prayer, nor His mercy from me. R. Abba the son of R. Hiyya b. Abba said to them: Thus said R. Hiyya b. Abba in the name of R. Johanan: Both of them are chastisings of love. For it is said: For whom the Lord loves He correcteth. Why then does it say: ‘And teaches him out of your law’? Do not read telammedennu, [you teach him] but telammedenu, [Thou teaches us]. Thou teach us this thing out of your law as a conclusion a fortiori from the law concerning tooth and eye. Tooth and eye are only one limb of the man, and still [if they are hurt], the slave obtains thereby his freedom. How much more so with painful sufferings which torment the whole body of a man! And this agrees with a saying of R. Simeon b. Lakish. For R. Simeon b. Lakish said: The word ‘covenant’ is mentioned in connection with salt, and the word ‘covenant’ is mentioned in connection with sufferings: the word ‘covenant’ is mentioned in connection with salt, as it is written: Neither shalt thou suffer the salt of the covenant of thy God to be lacking. And the word ‘covenant’ is mentioned in connection with sufferings, as it is written: These are the words of the covenant. Even as in the covenant mentioned in connection with salt, the salt lends a sweet taste to the meat, so also in the covenant mentioned in connection with sufferings, the sufferings wash away all the sins of a man.
It has been taught: R. Simeon b. Yohai says: The Holy One, blessed be He, gave Israel three precious gifts, and all of them were given only through sufferings. These are: The Torah, the Land of Israel and the world to come. Whence do we know this of the Torah? — Because it is said: Happy is the man whom Thou chastise, o Lord, and teach him out of Thy law. Whence of the Land of Israel? — Because it is written: As a man chastises his son, so the Lord your God chastises you, and after that it is written: For the Lord Your God brings thee into a good land Whence of the world to come? — Because it is written: For the commandment is a lamp, and the teaching is light, and reproofs of sufferings are the way of life.
Tractate Brachot p.5a