Children readily follow the example of their parents (at least to a certain age). Peter wants to say that believers are not just children of father Abraham (see Romans 4:16) but also of mother Sarah. For that reason the women of Peter’s day need to follow their mother’s example and “hope in God” to such an extent that they dare to submit to their husbands (1 Peter 3:5).
6 as Sarah obeyed Abraham, calling him lord. And you are her children, if you do good and do not fear anything that is frightening.