Let your peace return to you

If the home is deserving, let your peace rest on it; if it is not, let your peace return to you (Mt 10:13).

Here's an interesting passage. Normally, a phrase like "Peace be on your house" is just a social pleasantry, expressing the good will of the guest towards the homeowner. Like saying "I wish you all the best". 

These are ineffectual courtesies. A polite greeting. They don't cause what they wish or express. 

But here the idea seems stronger. If the disciples whom Jesus sends out as missionaries are rebuffed, then the gift of shalom returns to the disciples, as if Jesus granted the disciples the ability to confer an efficacious blessing on homeowners receptive to the Gospel. Not an impotent wish or expression of kind intentions. Rather, it makes an actual difference. 

Minimally, this means they won't experience an extra blessing of shalom. They will be in the same condition they were before they encountered the missionaries. 

However, the contrast might imply a curse. The alternatives are weal or woe. They will experience bane in place of blessing. They will be worse off. That makes sense.