good Samaritan 好心人；乐善好施者；行善者

【例句】
He acted as a good Samaritan, and took the poor woman to the hospital。
他乐善好施，把那可怜的妇女送进医院。

When my car broke down I would have been stranded if a good Samaritan had not stopped and offered me a lift.
我的车出了故障，要不是有一个好心人停下车，让我搭乘，我真不知如何是好。