Kabbalah su Proverbi 11:30

For the conversion of a particular convert, the soul flies out from that chamber, and enters under the wings of the Shechina. And She kisses it, since it is the fruit of the righteous ones, and sends it into that convert, and it steeps within. From that moment, they are called a "Ger Tzedek" (righteous convert). This is what the verse alludes to (Mishlei 11:30), "The fruit of the righteous is a tree of life." Just as the tree of life produces souls, so too the righteous person can produce fruit, by making souls.