משנה אויף ויקרא 15:1

A child’s cart is susceptible to the impurity of midras, and it may be handled on Shabbat, and it is dragged along only on matting. Rabbi Judah says: no vessels may be dragged along [the ground] except a wagon because it [only] presses [the earth] down.

But for [defilement contracted by] overhanging branches, or protruding stones, or a field that may have once been a cemetery, or land of the Gentiles, or the stone which covers the tomb or the supporting stone of a tomb, or a quarter-log of blood, or a tent, or a quarter-kav of bones, or utensils that have been in contact with a corpse, or on account of the days of counting [after contracting scale disease] or the days during which he is certified unclean [because of scale disease]; For all these the nazirite is not required to shave, but they do sprinkle him on the third and seventh [days], and [the defilement] does not annul the formerly served period, and he begins to resume counting [his naziriteship] immediately [after purification] and there is no sacrifice. In fact they said: the days of [defilement of] a male or female sufferer from gonorrhea and the days that a leper is shut up as a leper count toward his [naziriteship].