The Gemara (Yoma 9b) [inquires]: "Since in the time of the Second Beis HaMikdash the Jewish people were engaged in the study of Torah, the performance of mitzvos and acts of lovingkindness, why was it destroyed?" [Answers the Gemara:] "Because sinas chinam was prevalent among them." Thus, it is possible for sinas chinam to coexist even with Torah study and the performance of mitzvos, and even with loving-kindness.

[Another reason for the Destruction is offered] in the Gemara (Bava Metzia 30b): "Because they acted strictly according to the requirements of the law, without going beyond the letter of the law." Tosafos explains [the apparent contradiction between these two quotations by saying]: "Both causes were responsible [for the Destruction]."

Thus, lack of Divine service beyond the letter of the law, this manner of service being known as middas chassidus - "the conduct that befits a chassid" (Cf. ibid. 52b and Chullin 130b), as well as sinas chinam [are so injurious,] that even when people are engaged in the study of Torah, the performance of mitzvos, and acts of lovingkindness, the Destruction of the Beis HaMikdash can still be brought about. [The same applies, in a more personal vein, to] the destruction of the sanctity [- the personal Beis HaMikdash] within each and every Jew, as shall soon be explained.

The sin of sinas chinam is unfortunately all too common among those who are actively involved in Divine service: each individual regards himself as an autonomous entity, placing complete faith in his own judgment and desire, without allowing any leeway at all for the judgment of another. Such an individual insists on his own interpretations in the study of Torah, and on his personal perceptions of Divine service. Thus those involved in Divine service do not coalesce and unite at all.

Truly, it is of fundamental importance that those who are involved in the study of Torah and in Divine service should bond together and speak with one another. For then, not only will each help rouse the other to establish set times for Torah study and conceive new ideas as to how to increase the number of participants in Torah classes, but it is also beneficial for their own study of Torah [and Divine service] as well.

[With regard to the manner in which it benefits Torah study,] there is the statement of our Sages, of blessed memory (Taanis 7a): "R. Chama bar Chanina said: 'What is the intent of the verse (Mishlei 27:17), "Iron sharpens iron"? It seeks to tell you that just as one piece of iron sharpens the other, so too do two Torah scholars each sharpen the other['s understanding through their discussions] in Halachah.'"

Neither of them can claim a monopoly on the truth of his interpretations. Only when they hear each other's opinion and engage in dialectical discussion, are they able to arrive at the true meaning of the subject at hand.

The same is true with regard to Divine service, wherein "one person sharpens the other": considerable benefit is derived from two friends' revealing their faults to each other and discussing them.

Summary: Sinas chinam destroys both the general and the personal Beis HaMikdash. Uniting and speaking with one another is fundamental to Torah study and Divine service.