We have now entered a period of time – the three weeks between 17 Tamuz and 9 Av – when we recall the events leading to the destruction of the First Temple in 586 BCE. Added to that is the destruction of the Second Temple in 70 CE and other tragic events, such as the expulsion from Spain in 1492. There are different customs observed at this time, some more strict than others, and there are those (this writer included) who question how much mourning there should be at this time when Jewish sovereignty has been restored and Jerusalem is hardly the abandoned, destroyed ruin depicted in so much of the liturgy and dirges written to be recited in this period.From a historical point of view, there is a dispute as to whether Tisha Be’av was observed during the period of time between the return to Zion from Babylonia and the destruction of the Second Temple. After all, the prophet Zechariah had predicted that these days of mourning would become “occasions for joy and gladness, happy festivals for the House of Judah” (8:19) when the Temple would be rebuilt – as it was. Should there not be a similar recognition of what has happened in this time as well, at the very least a relaxation of some of the mourning customs? The question of what brought about the catastrophe of the year 70 CE preoccupied the minds of the sages. The writings in the Bible are quite clear about the reason for the destruction of the First Temple. The prophet Jeremiah spent his entire career predicting what would happen if the people of Judea did not abandon their wickedness and return to the ways of the Lord. “…if you execute justice between one man and another; if you do not oppress the stranger, the orphan, and the widow… then only will I let you dwell in this place…” (Jeremiah 7:5).The problem in the year 70 CE was that the sages saw clearly that that generation was not guilty of such fundamental transgressions as murder and idolatry. Why then did God punish them, they asked. They were also very aware that the true cause of the destruction was insistence on confronting the might of the Roman Empire when there was not the slightest chance that they (the Jews) could prevail.The greatest of the sages at that time, Rabban Yohanan ben Zakkai, opposed the rebellion. “My children,” he asked, “why do you destroy this city and why do you seek to burn the Temple? …All he [Vespasian] asks of you is one bow or one arrow and he will leave you alone!” (ADRN A 4). Had he prevailed against the hotheads of the various zealot groups, there would have been no catastrophe and all of Jewish history would have been very different – and probably much better and more successful.In searching for a moral that could be taught by the event, the sages seized upon “causeless hatred” – the fact that people and groups did not love or respect one another – and taught that that was the reason for the destruction. “The Second Temple… fell because of causeless hatred – a sin that is as severe as idolatry, harlotry and murder” (Yoma 9b). With no good reason, they hated one another. Instead of love and unity among Jews, there was hatred and bickering. “The hatred of others is a terrible sin before God” (Tosefta Menahot 13:22). I suppose there was even a certain historical basis for this in that the rebels against Rome were not united, but were constantly warring against one another, as well as against Rome.Be that as it may, we must admit that the sages found a sin that is worth speaking against and trying to eliminate from Jewish life. The recent events in Israel concerning relations between Israeli Jewry and the American Diaspora are a good example of how this sin of causeless hatred continues to beset Jewish life. I do not want to repeat any of the things that were said recently by prominent rabbis and government ministers about groups within Judaism with whom they disagree. They were beneath the dignity of people who hold such offices. Their inability to disagree respectfully, rather than making outrageous statements and using unforgivable epithets, is truly beyond belief. Have they – have we – learned nothing over the centuries? Are we bound to repeat the sin that the sages spoke against – causeless hatred – again and again? If there is anything that we should do during these three weeks, it is to battle against Jewish disunity, against the lack of respect for others, against causeless hatred. If we do not succeed in eliminating that, we will indeed have a good reason to mourn. ■ The writer, a two-time winner of the Jewish Book Award, is a past president of the International Rabbinical Assembly and a member of its Committee on Jewish Law and Standards. His latest book, Akiva: Life, Legend, Legacy (JPS) will soon be published in Hebrew by Yediot Press and the Schechter Institute.