Our Sages ordained that a person who distributes his money to tzedakah may not spend more than a fifth of his wealth on charity, lest he become poor and he will be forced to rely on the generosity of others himself. However, it may be inferred from the words of the poskim (halachic decisors) that a very wealthy person may distribute even more than a fifth to tzedakah and that this rabbinic rule does not apply to him. Also, it is permissible to distribute more than a fifth to tzedakah when the person approaches his death, for at that stage the concern that the person himself “may become impoverished” no longer applies.
