Three gifts to the kohen come from a Jews sheep. If it is a male firstborn, it must be given to the kohen who offers it as a sacrifice and eats its flesh. When a sheep to which the kohen is not entitled is slaughtered, certain portions of it go to the kohen. And, finally, when a Jew shears his sheep he must give the kohen a portion of the wool.

The difference between them is that the first two gifts apply to even a single sheep while the gift of wool is incumbent on the sheep owner only when he shears at least five sheep.

How do we know that there is a minimum of five when all the Torah says is to give the kohen from "the shearing of your sheep" (Devarim 18:4) without specifying a number?

The answer lies in a passage (Shmuel I 25:18) describing the gift which Avigail, the wife of the wicked Naval, prepared for David to dissuade him from slaying her husband who had so offended the anointed future king of Israel. One component of that gift is described as "five prepared sheep".

The literal meaning of this phrase is that the sheep were prepared for the eating of David and his men. Rabbi Ashi, however, saw in the choice of the word "prepared" a hint that this number of sheep "prepared" their owner with the opportunity to fulfill a mitzvah not previously available to him. This could not refer to the mitzvot of the firstborn or gifts of meat because they apply to even a single animal as is evident from the passages dealing with them (Bamidbar 18:17 and Devarim 18:3). The passage concerning the wool shearing, on the other hand, speaks of sheep in the plural form, allowing us to conclude that the mention of five which prepares a Jew for a new mitzvah refers to this mitzvah, and that the obligation comes only when one shears at least five sheep.

• Chullin 137a

When does involvement in performing a mitzvah provide Divine protection from danger?

This is a question that arises from an incident related in our gemara. Rabbi Yaakov witnessed a scene in which a father asked his son to climb a ladder to a high perch and there fulfill the mitzvah of sending away the mother bird before taking her fledglings, the commandment which is the central subject of this the final perek of Mesechta Chullin. The son did as requested and sent away the mother bird. But as he proceeded down the ladder with the fledglings in hand, he fell off the ladder to his death.

How could this happen, asks the gemara, when we have a guarantee that those performing a mitzvah are safe from danger both coming and going, and here we have a boy who was doing the double mitzvah of honoring his father and sending away the mother bird?

The answer given is that the ladder used was a rickety one which presented a high risk for anyone climbing it, and when such high risk is involved one cannot rely on the protection of a mitzvah.

The source for this is the response of the Prophet Shmuel to G-ds command to anoint David as King of Israel after His disappointment with the performance of Saul in that role. "How can I go", said Shmuel, "when if Saul hears of this he will slay me." (Samuel I 16:2) Although Shmuel was certainly involved in doing the mitzvah of obeying G-ds command, he hesitated to rely on the protection it provided when there was such a high risk. G-d agreed with his caution and provided him with a cover for his mission.

• Chullin 142a