Now you are a fish

A Jewish guy finds out that a Christian priest gives $500.00 to give whoever wishes to convert. 
So he goes to the priest and he does stuff to him and then finally he tells him "Now you are Christian, but you need to promise me that you cannot eat meat for dinner on friday". 
He says OK and goes home happy, and yells to his wife and says now we are rich, we have money now and we can spend it on anything. 
There comes friday night and they have food in the oven and cooking, the priest wants to make sure the guy does what it takes to be a Christian, he goes to his house. After all the introduction he goes to the oven and sees a brisket there, he turns to the guy, and says "i thought i told you that you cannot have any meat." 
The Jewish guy tells him "that's not meat that's fish." 
He says "i see meat." 
"Well" the guy says "when i came to you, you put your hands in some water and splash my face and told me that now i am christian. So i splashed my hands in front of the meat and told him now you are a fish... so we are having a fish."