I wanted to know if there is a specific word for the person who is/the act of **willingly taking the punishment of another person** who is convicted of a crime so that they don't need to face the punishment. 

For example, 

> 
> Jesus willingly took the punishment of the sins of mankind by dying on the cross for them. 
> 
> 
> 

Here what is the single word for this act and how we can distinguish Jesus in this context?