Siman 477

(34.) Long before the Land of Israel — someone asked him about children. And he told him to give charity. He replied that he could not afford it. And he told him to have faith — for faith counts as charity. As it is written about Abraham [Genesis 15]: "And he believed in G-d, and He counted it to him as righteousness." And he said: "Through faith one merits children — for emunah [faith] in gematria equals banim [children]." And so it came to pass that this man was blessed and had children.