A goyishe professor bought two slices of kosher pizza for me and treif pies for the rest of my law school class. When the goy hands me the kosher box of pizza, am I allowed to believe him that it is kosher?
The name of the pizzera is on the box, which I know is a kosher place. Other than that, there is no seal. Is the pizza permitted?
I would say – If the goy were hungry, he could take from the non-kosher pies.
It doesn’t make sense that he would go to a kosher place (which he clearly did, based on the box), buy kosher pizza, eat it himself, and then put non-kosher in the box and lie to me! If he were hungry, he would just take from the non-kosher pies.
Should I demand to see a receipt (which would be very uncomfortable)?
P.S. I already ate one slice of the pizza and now have one left. Do I need to do teshuva? Can I eat the remaining slice?
Since the box displayed clearly that it came from a kosher place and the professor is not gaining anything by switching it with a non kosher pizza you can eat it. Also the profeessor is afraid that you might go to the kosher place and asked them if he purchased the pizza from them. Bon appetite!
Y:D 118:7&10 also Taz 10, Teshuvas Mabit 1:208