This chain alludes to the Torah's descent throughout all generations of history. Due to the decline of the stature of the generations, it is incumbent upon us to become increasingly scrupulous regarding Torah and Mitzvos. The further the generations are removed from the giving of the Torah, the more care is needed to preserve its integrity. Therefore, the first Mishnah concludes by telling us to "make a fence around the Torah," Ceaseless vigilance is the one way we can be sure to maintain our connection to the Torah. Hence, the sages of ensuing generations enacted laws, such as "fences," to ensure the preservation of the Torah. The fact is that these "fences" have the same power as the Torah itself, which "Moshe received from Mount Sinai."
This same idea hinted at the beginning of Pirkei Avos, is also alluded to at its conclusion. These Beraysos, despite being outside the Mishnah, were "taught by the Sages in the language of the Mishnah." This is to demonstrate that they are the equivalent of the Mishnah. They have the same force as the rest of the Torah, which "Moshe received from Mount Sinai."
(Adapted from a talk given on Shabbos Mevorchim Hachodesh and Erev Rosh Chodesh Sivan, 5749)
