Tractate Avot of the Mishnah is generally dated in the third century and is considered the basic text of rabbinic Judaism. The present commentary proposes a critical re-evaluation of this position. The commentary obviously tries to interpret the individual sayings of Avot as to their literary characteristics, their cultural context and their original meaning. But above all it tries to contextualize the tractate within rabbinic literature, to analyse its language/phraseology and to trace its earliest evidence and its use in later rabbinic literature. This approach will demonstrate that some sayings are well known even outside Avot already in the earliest rabbinic tradition, but that many other sayings do not reflect general rabbinic theology and seem to be almost unknown in rabbinic tradition before the late eighth century. This leads to the conclusion that only a kernel of the text existed already in the time of the Mishnah; its greater part grew in the following centuries. Only in the eighth century the tractate as we know it, reached its nearly final form and became soon popular due to the introduction of its text into the reading of the synagogue.