One who buys from a householder, and then buys from him a second time, may tithe from this [purchase] on behalf of that [one], even [if they are] from two boxes, [and] even [if they are] from two towns. [If] a householder was selling vegetables in the market: When they bring him from his [own] gardens, [the buyer] may tithe from one [purchase] on behalf of all; [when they bring him] from other gardens, he must tithe from each and every one.