On the website under misconception, the following is said: Misconception 1: It is not permissible to trim/cut hair or nails while menstruating.
Busted: Whilst it is somewhat disliked (makruh tanzihi) to cut hair or nails in a state of major ritual impurity due to wet dreams, intercourse, etc. (janabah), there is no dislike in doing so during menstruation (hayd) or post-natal bleeding (nifas).
Is there any ‘Ibaraat that explicitly stated this?
In the name of Allah, the Inspirer of truth
In many books of fiqh, cutting nails or removing hair has not been considered amongst restrictions for a person in the state of major ritual impurity. However, in Fatawa Hindiyya quoting from the Ghara’ib, it is mentioned that to cut nails or remove hair in the state of janaba is disliked. It should be noted that since the Ghara’ib is not a relied upon text, at the most the ruling for hair removal or cutting nails can be considered makruh tanzihi and not taḥrimi.
As for cutting hair or trimming nails during hayd or nifas, these situations are different to janaba considering they cannot be overcome on one’s own accord; rather they remain until the ceasing of legal blood (dam sahih). Hence, the restriction in janaba for cutting hair or trimming nails will not be extended to hayd or nifas.
And Allah knows best.
الفتاوى الهندية (5/ 358) حلق الشعر حالة الجنابة مكروه وكذا قص الأظافير كذا في الغرائب.