Imam Hasan, may Allah have mercy on him, said: The woman experiencing irregular bleeding (mustahadah) will observe the waiting period (‘iddah) according to the calculation of her menstruation.

It is narrated from Imam Awza'i, may Allah have mercy on him, that I asked (Ibn Shihab) Zuhri, may Allah have mercy on him, about a man who divorced his young wife; she used to menstruate but at the time of divorce her menstruation stopped and she did not see any blood. So what will be her waiting period ('iddah)? He replied: Three months.

Imam Awza'i (may Allah have mercy on him) said: And I also asked Imam Zuhri (may Allah have mercy on him) that a man divorced his wife, she experienced menstruation twice and then it stopped, so how many days will she observe 'iddah? He replied: Her 'iddah will be one year.

It was also said: I asked Imam Zuhri, may Allah have mercy on him, about this: A man divorced his wife who used to menstruate, and she waited for three months (i.e., did not menstruate), then she menstruated once, then (after coming once) her menstruation stopped and she sat for seven or eight months (without menstruation), then she menstruated a second time. The first time it came quickly, the second time it came after a long delay. So how will she complete her waiting period (‘iddah)? He said: If her menstruation comes irregularly at different times, then her waiting period will be one year.

Imam Awza'i, may Allah have mercy on him, said: If divorce takes place and menstruation occurs once a year, then what will be the duration of the waiting period ('iddah)? He replied: If she used to have menstruation and purity at their appointed times, then in our opinion, she will observe the waiting period of menstruation.

It is narrated from Imam Awza'i, may Allah have mercy on him: I asked Imam Zuhri, may Allah have mercy on him: If a man buys a minor slave girl, who cannot become pregnant like her peers, then what will be the period of her 'Istibra' (waiting period for womb's clearance)? He replied: Three months.

Yahya bin Abi Kathir said: The period will be forty-five days.

Sayyiduna Ibn Abbas (may Allah be pleased with them both) used to say regarding a woman with continuous bleeding that she should perform ghusl for every prayer, then offer the prayer.

Hammad said: If a woman experiencing istihada (non-menstrual bleeding) does not pray for several months due to ignorance, then she must make up all those missed prayers. It was asked: How will she make them up? He said: If she has the strength, she should make up all the missed prayers in a single day. Imam Darimi, may Allah have mercy on him, was asked: Do you also say this? He replied: «أي والله» (Yes, by Allah, I also say this).