It shows that tigers are fierce and cruel, but they don't eat their own children. It is a metaphor that everyone has the heart to love his son and the feeling of flesh and blood.
The source is Wei's "Dragon Story Hidden Springs": "Your father was in Luoyang and didn't go home for a while. When I wait another day, I will persuade him slowly. Tiger poison does not eat children, and children should not be short-sighted. "
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Related Baidu "Tigers don't eat children"