Shekalim 21 - Found spittle

When people were able to keep the laws of ritual purity, they were careful if they found spittle, for perhaps it came from someone (a zav) whose spittle would make a person ritually impure. However, in Jerusalem, people kept a higher standard, so spittle found there was considered pure - this is Rabbi Meir's opinion. Rabbi Yose, however, says that this depends on traffic. In the time of the festivals, when ritually pure people occupied the center of the streets, spittle found in the center was pure, but one on the sides - impure. On other days it was the reverse. The Talmud then discusses knives found on the way down to a mikveh, and on the way up from it, at different times and for different types of knives.

Rav Bisna wanted to know if the blood of killed animals makes one ritually impure and what amount of it, and he posed this question to Rav Bivi. However, Rav Bivi did not answer and even spurned Rav Bisna. Rav Bivi' colleague, Rav Zerika, asked him, “Is it because he asks you a question that you spurn him?” Rav Bivi replied with the phrase from the Torah, “Your life will hang in suspense” - is one who only has provisions for a year, and “you will not be sure of your life” is one who eats from hand to mouth and buys his food from the baker daily. Rav Bivi said that it applied to himself. This is why he did not have the presence of mind to answer.

Art: A partridge, a dead duck, a pitcher, two knives, a loaf of bread and hens, on a forest floor By (after) Ferdinand Phillip De Hamilton