Babylonian Talmud Gittin 55b

The destruction of Jerusalem came through a Kamza and a Bar Kamza in this way. A certain man had a friend Kamza and an enemy Bar Kamza. He once made a party and said to his servant, Go and bring Kamza. The man went and brought Bar Kamza. When the man [who gave the party] found him there he said, See, you tell tales about me; what are you doing here? Get out. Said the other: Since I am here, let me stay, and I will pay you for whatever I eat and drink. He said, I won't. Then let me give you half the cost of the party. No, said the other. Then let me pay for the whole party. He still said, No, and he grabbed him in his hands and put him out. Said the other, Since the Rabbis were sitting there and did not stop him, this shows that they agreed with him. I will go and inform against them, to the Government. He went and said to the Emperor, The Jews are rebelling against you. He said, How can I tell? He said to him: Send them an offering and see whether they will offer it [on the altar]. So he sent with him a fine calf. While on the way he made a blemish on its upper lip, or as some say on the white of its eye, in a place where we [Jews] count it a blemish but they do not. The Rabbis were inclined to offer it in order not to offend the Government. Said R. Zechariah b. Abkulas to them: People will say that blemished animals are offered on the altar. They then proposed to kill Bar Kamza so that he should not go and inform against them, but R. Zechariah b. Abkulas said to them, Is one who makes a blemish on consecrated animals to be put to death? R. Johanan thereupon remarked: Through the scrupulousness of R. Zechariah b. Abkulas our House has been destroyed, our Temple burnt and we ourselves exiled from our land. [Soncino translation]