Dear Rav Kornfeld,

This concerns the well-known principle on this Daf that one's income is decided on Rosh HaShana till the next, excluding expenses for Shabbosos and Yomim Tovim.

Sefer Pele Yoetz in section "Kesef'' says similarly that a person cannot make even a prutah more or less than was decreed for him, excluding (acc. to him) expenses for Mitzvos and Ma'asim Tovim where if one spends more, he is given more. I was wondering why the Pele Yoetz extends the rule of ''Im mosif mosifim lo'' to "Mitzvos and Maasim Tovim.'' Is there another source in Chazal upon which he based this?

And, if so, "Mitzvos and Maasim Tovim'' is a very big field. I'm wondering what is the criteria governing for which Mitzvos and Maasim Tovim he is referring to, that one's expenses in connection with them are not included with his yearly income decreed on Rosh HaShana? (For example, would Mezuzos, Tefilin, Tzedeka fit in to this?)