Comentario citado sobre Levítico 5:16

וחמישתו יוסיף עליו, “and he is to add a fifth of it” (the value of the stolen property); if his confession is not the result of witnesses having accused him of his guilt, but it is simply an expression of his remorse, then he pays only this extra 25%, but if witnesses testified about the theft he is required to add a second 25% as a penalty. We have already explained in our commentary on Leviticus 5,16 precisely what is meant by this.

ויתנבאו ולא יספו, “they prophesied;” but they did not continue to do so with the help of Moses. The word: יספו is to be understand as if the Torah had written “they added,” the word is used in this sense also Leviticus 5,16 ויסף חמישתו עליו “ “he will have to add a fifth of it in addition