To tolerate or encourage evil or bad practices, only to suffer the harm or consequences oneself eventually; to harbor a viper in one's bosom.
他长期对那些不良风气视而不见，结果真是关门养虎，虎大伤人，最终影响了整个项目的顺利进行。
He had long turned a blind eye to those negative trends, which truly became a case of "raising a tiger that would eventually harm him," ultimately affecting the smooth progress of the entire project.
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