Rebbi says: What is the intent of "with a rod"? It is "extra" towards the formulation of an identity (gezeirah shavah), viz.: it is written here "rod," and, elsewhere, (vis-à-vis tithing, Leviticus 27:32) "rod." Just as here, excluding (a servant) acquired by two partners, so, there, excluding (from the tithe a beast) acquired by two partners.