A girl divorced before reaching menstruation: what waiting period does she observe?

Ibrahim, al-Sha'bi and al-Hasan said concerning a young girl who is divorced before she has reached the age of menstruation: She observes the waiting period by months. If she menstruates before the months have passed, she restarts the waiting period by menstrual cycles; and if she menstruates after the months have passed, her waiting period is complete.

Something similar is reported from al-Sha'bi.

It is also reported from al-Hasan concerning a young girl who is divorced before she has reached the age of menstruation; they said: She observes the waiting period by months. If she menstruates before the months have passed, she restarts the waiting period by menstrual cycles; and if she menstruates after the months have passed, her waiting period is complete.

Ibrahim (may Allah have mercy on him) said: If a man divorces a young girl who has not reached menstruation, she observes a waiting period of three months. If she menstruates before the three months are complete, her waiting period (by months) is cancelled, and she now observes the waiting period afresh by menstrual cycles.

Jabir bin Zayd (may Allah have mercy on him) was asked: A young girl was divorced by her husband after consummation, while she did not menstruate. She had observed a waiting period of two months and twenty-five days when she began to menstruate; what should she do now? He said: Now she should observe a waiting period of three menstrual cycles.

Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said the same.