I have noticed that when I give money to people who collect in shul, they often respond by saying "tizkeh l'mitzvos."
Are there any sources before relatively recently for using this phrase?
Mi Yodeya is a question and answer site for those who base their lives on Jewish law and tradition and anyone interested in learning more. It only takes a minute to sign up.Sign up to join this community
I don't know when common usage of this phrase began. However, from reading various articles, it appears to have been in common usage for many decades. This article seems to support the notion that at least the concept supporting the expression is from Pirkei Avot 4:2 where Ben Azai says that one should be careful to perform every "type" of mitzvah - both "easy" and "difficult" ones, because one mitzvah "pulls" (or instigates) another mitzvah, and the reward of a mitzvah is (another) mitzvah.
Rav Bartenura, in his commentary, explains the concept of the "reward" part, in that when one performs a mitzvah, in heaven, another mitzvah is prepared for that person so that the person may receive reward for both of them.
So, I gather that the idea behind the wish "tizkeh lemitzvot" is in line with Rav Bartenura's explanation. When you give tzedaka (though, the wish is not limited to hearing this from tzedaka recipients), the person is using the plural form "mitzvoth" as a hint that you should merit to be able to perform another mitzvah and receive the reward for both the tzedaka giving as well as the next mitzvah.