Then the Lord tells Moses that if people swear to G_d falsely they should pay the injured party what they owe, plus one fifth. We see often that one fifth is added to a debt.
And if there is no one to give the restitution to them it shall go to the kohen, unless there is a kinsman of the injured. And the first fruit of the season should be given to the kohen.
In the commentary it says, ““Everyone’s holy things belong to him,” which informs us that their benefit [to give them to whichever kohen it pleases him] belongs to the owner. They [the Sages] deduced many other expository explanations from it [this clause] in the Sifrei (Naso 1:31-34). An Aggadic interpretation: “Everyone’s holy things belong to him” [means,] if one withholds his tithes and does not give them [to the kohen or Levite], those tithes shall be his, for eventually his field will produce only a tenth of its usual yield.”
This is interesting in terms of the karmic effect of not tithing.