Who knows sixty-seven?
Please cite/link your sources, if possible. At some point in the next few days, I will:
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Go on to the next number.
A Nazir who was a confirmed Metzora (muchlat), but possibly tamei, cannot resume drinking wine and becoming tamei until at least 67 days have passed (Nazir 60b). See the commentators there for the details.
According to the Rambam (Hil. Sefer Torah ch. 8), the Song of Haazinu should be written in 67 lines in a Sefer Torah.
(I believe that the Yemenite communities still do so; most other traditions have 70 instead. But I have a feeling we'll have a lot more "70 mi yodeya"s than 67s...)
The Gemara in Bechoros 8a states that a carob tree takes 70 years from the time it is planted until its fruits develop, and the "gestation period" of the fruit (i.e., the span between when the flowers emerge and when the fruit develop -- Rashi) is three years. Hence, it takes 67 years for a carob tree to flower.
A muzuzah's position is at the beginning of the top third of the doorway -- 67% (rounded) of the doorway's height, as measured from the floor.