What is the punishment for a father who tells his children they are children of illegitimacy (awlād al-ḥarām)?

A Muslim should accustom his tongue to good speech, especially a father, because children take him as a role model, and he should avoid obscene words. A father's statement to his children that they are "children of haram" (illegitimate) is considered an ugly expression. If he intended thereby to accuse them of fornication (qadhf), then it is forbidden and necessitates the prescribed punishment (hadd). If he only intended it as an insult or revilement, it is not considered qadhf. This depends on customary usage and contextual evidence.