Don’t throw the baby out with the bathwater
Don’t get rid of important things with the unimportant.
In the 1500’s people would often bath once or twice a year. In families, the adult male would go first, then the women and then the eldest child and then so on. Eventually, the baby would be left in bathwater that was often totally filthy. The idea being that the mother would mistakenly throw the child out along with the water. People weren’t that stupid back then were they?