《后汉书·列传·皇甫张段列传》
河西的风俗多妖怪禁忌，凡是二月、五月生的儿子以及与父母同月生的，都要杀掉。
其俗多妖忌，凡二月、五月产子及与父母同月生者，悉杀之。
The customs of Hexi were full of demons and taboos. Any son born in February or May, or with the same month as his parents, was killed.