We derive from Avshalom who was a nazir olam that if one's hair gets too long, one can trim it. But at what intervals did Avshalom cut his hair? Three opinions are brought and the GEmara both raises questions and explains these three approaches. If one accepts to be a nazir without specifying how much time, the Mishna rules that the timeframe is thirty days. Rav Matna learns this from gematria of the words "yihiye." Bar Pada derives that is it twenty-nine from the twenty-nine times in the chapter where the root n.z.r. appears. Two Mishnayot are brought to question Bar Pada but are resolved. After explaining the second one, that source is thrown back against Rav Matna. After that is resolved, another Mishna is brought to raise a difficulty against Bar Pada.