TB Yevamot 62b

Rabbi Akiva had 12,000 pairs of students, from Gevat to Antipars. They all died in one period of time, because they did not treat each other with respect. The world was desolate of Torah until Rabbi Akiva came to the Rabbis in the south and taught the Torah to them. These Rabbis were Rabbi Meir, Rabbi Yehuda, Rabbi Shimon, and Rabbi Elazar ben Shamua. These Rabbis perpetuated the study of Torah at that time.

A Tanna taught: The 12,000 pairs all died between Pesach and Shavuot. Rav Chama bar Aba said (others say Rav Chiya bar Avin said) that they all died a painful death. What was it? Rav Nachman said it was ‘askera’.

Vayikra 18,19

You shall not take revenge, nor shall you bear a grudge against the members of your people; you shall love your neighbour as yourself - I am the L-d.

Torat Cohanim ibid

‘And you shall love your neighbour as yourself’ - said Rabbi Akiva, this is a great principle in the Torah

TB Pesachim 49b

It was taught in a beraita: Rabbi Akiva said, when I was an am-haaretz I said, ‘who will give me a talmid chacham so that I can bite him like a donkey?’ His students said to him, Rabbi, why did you not say ‘like a dog’? He replied, a donkey bites and breaks bones, while a dog bites and does not break bones.

TB Yoma 9b - discussion of why the second Temple was destroyed

In the second Temple period, people occupied themselves with Torah, mitzvot and acts of kindness. So why was the Temple destroyed? Because of the sinat chinam (causeless hatred) which existed. This teaches that causeless hatred is equated to the three cardinal sins of idolatry, immorality and spilling of blood.

Introduction to the Netziv’s commentary on the Torah

(with regard to the generation of the destruction of the second Temple)…we explained that they were righteous, pious and toiled in Torah. But they were not upright in their approach to the world. Therefore, because of the causeless hatred in their hearts for each other, they suspected that people whom, in their view, acted differently from them in respect of the fear of G-d, were Sadducees or heretics. As a result, society came to bloodshed through such divisions (like the generation of the flood?) and all the bad things that happened to the world until the Temple was destroyed…G-d is ‘upright’ and only countenances righteous people who act in an upright way in their worldly dealings, and not in a twisted way, even if they are acting for the sake of Heaven, because this demolishes the creation, and destroys the settlement of the world.

TB Shabbat 33a-34a (selections)

The Rabbis taught: a sign of causeless hatred is jaundice…a sign of lashon hara is askera…Rabbi Shimon said askera is a consequence of neglecting Torah study…Rabbi Gurion said (some say it was Rav Yosef the son of Shemeya), in a time when there are righteous people in the generation, they are caught by the sins of that generation…

Rabbi Yehuda, Rabbi Yossi and Rabbi Shimon were sitting together and Yehuda ben Gerim was with them. Rabbi Yehuda praised the Roman infrastructure in Israel…Rabbi Shimon bar Yochai said, everything that they built was only for their own needs…The Romans heard of this, and said that Rabbi Shimon should be killed for denigrating the Romans.

Rabbi Shimon and his son Rabbi Elazar went and hid in beit midrash. Every day, Rabbi Shimon’s wife bought them bread and water, until the search intensified. Rabbi Shimon feared the Romans would torture his wife, so they went and hid in a cave. A miracle occurred and a carob tree and spring were created for them. They shed their clothes and sat in sand up to their necks.

All day, they studied together, but when it was time to pray, they dressed, covered themselves, and prayed. Afterwards, they took off their clothes and hid in the sand, to avoid wearing out their clothes.

They stayed in the cave for 12 years. Then, Eliyahu Hanavi came and stood at the entrance to the cave. He said, who will tell Bar Yochai that Caesar had died, and that the decree has been rescinded? Rabbi Shimon and Rabbi Elazar, on hearing this, left the cave.

As they returned to the rest of society, they saw some people who were ploughing a field and sowing crops. Rabbi Shimon declared, these people are forsaking the world to come and busying themselves instead with the ephemeral concerns of this world!

Wherever Rabbi Shimon and Rabbi Elazar looked, the focus of their vision would immediately burn. An Heavenly voice rang out and said to them, have you come to destroy My world? Return to your cave. They stayed there for another 12 months.

The next time they emerged from the cave, Rabbi Elazar would destroy with his fiery look, but Rabbi Shimon would heal the damage. He said to Rabbi Elazar, my son, the world has enough of the sort of you and me.

Close to Shabbat, one Friday afternoon, they saw an old man holding two bundles of myrtle, running home as the sun descended. They asked him why he had these. He answered that they were in honour of Shabbat…one for zachor (sanctification of Shabbat) and one for shamor (cessation of prohibited labours). Rabbi Shimon said to his son, see how precious the mitzvot are to the Jewish people! They were appeased.

Michtav M’Eliyahu 5:266 (Rabbi E.E.Dessler)

One who truly mourns for Jerusalem must try and engage in its rebuilding. Jerusalem was destroyed because of sinat chinam and bitul Torah - i.e. these were the destruction (chorban). The focus was spiritual destruction. If so, how does one build Jerusalem? From this will come the blessing of each person sitting under their vine… Love of others and study of Torah…one who does not attempt to build spiritually is instead engaged in building himself, not Jerusalem.

Rabbi Avraham Hacohen Kook is said to have either coined or popularised the phrase ‘ahavat chinam’ - causeless love.