贫贱之交不可忘 pínjiànzhījiāobùkěwàng one should not forget friends from poor times
A friend made during times of poverty and hardship should never be forgotten; usually paired with [[糟糠之妻不下堂|糟糠之妻不下堂|zao1 kang1 zhi1 qi1 bu4 xia4 tang2]] to emphasize not abandoning those who shared one's struggles