You cannot get blood out of a stone 英文諺語
You cannot get blood from a stone 石頭擠不出血來；鐵石心腸那有淚
You cannot get help from an uncharitable person or money from someone who has none. Attempting the impossible and expecting results, usually revolving around the collection of a debt that cannot be paid. Something that cannot be obtained, regardless of how much force or persuasion is used.
Barry and Tim spent two hours trying to convince the old man to contribute to the children’s hospital. Eventually, Barry turned to Tim and said in disgust, “This is hopeless. We can’t get blood from a stone.”