The maaseh behind it
It is brought in the Gemara (Bava Basra 11): Binyomin Hatzaddik was in charge of the kupah shel tzedakah. In a year of drought a woman came to him and said "Rebbi, parneseni." He told her he swore there was nothing left in the kupah; she answered that if he would not support her, she and her seven children would die. He gave her from his own pocket and fed them. Years later he fell ill and was about to be niftar at thirty-five. The malachei hashareis said before the Ribbono shel Olam: "You said that whoever sustains one nefesh from Yisroel is as if he sustained a whole world — and Binyomin Hatzaddik, who kept alive a woman and her seven children, should die in the best of his years?" On the spot they tore up his gezar din and added him another twenty-two years.