The Segulah of Giving One-Fifth to Charity

Sefer Ach Pri Tevuah sees from this verse a hint to the idea that one should give a fifth of his income to tzedakah. If one does this, he will merit seeing much blessing from the remaining four-fifth. He concludes by saying: “Every Jew who gives one-fifth of his possessions to tzedakah will certainly have all goodness now and forever.”

וּנְתַתֶּם חֲמִ ישִׁ ית לְפַרְ עֹה וְאַרְ בַּע הַיָּדֹת יִהְיֶה לָכֶם לְזֶרַ ע הַשָּׂדֶה וּלְאָכְלְכֶם וגו' (מז, כד)
And you shall give a fifth to Pharaoh, and four parts shall be yours for seed for your fields, for your food... (47:24)