I.
The time limit for shaving the pubic hair has been soundly narrated; it is not to be left for more than forty nights.
It was narrated that Anas ibn Malik said: A time limit was set for us for trimming the moustache, cutting the nails, plucking the armpit hairs and shaving the pubic hair: that was not to be left for more than forty nights. Narrated by Muslim, 258.
An-Nawawi (may Allah have mercy on him) said:
What is meant is: do not leave it for more than forty nights.
The phrase “A time limit was set for us” come under the heading of marfu` hadiths, like the words “We were instructed to do such and such.” It was narrated somewhere other than in Sahih Muslim: The Messenger of Allah (blessings and peace of Allah be upon him) set a time limit for us. And Allah knows best.
End quote from Sharh Sahih Muslim, 3/150.
The wisdom behind that is maintaining cleanliness and good looks.
Ibn al-Jawzi (may Allah have mercy on him) said:
In the hadith, it says: “A time limit was set for us for trimming the moustache, cutting the nails, plucking the armpit hairs and shaving the pubic hair: that was not to be left for more than forty nights.”
You should understand that if more time is added to that, dirt will accumulate and may gather under the nails in such a way as to prevent water from reaching the skin [when doing wudu’ or ghusl], in addition to the fact that it makes the nails no longer look nice, which is something that is required with the nails and moustache.
End quote from Kashf al-Mushkil, 3/313.
II.
Setting the limit of forty nights is the maximum time. It does not mean that it is recommended to leave these things for forty nights and then remove them; rather the best is to pay attention to them and trim them before forty nights, if they grow long.
Ibn Hubayrah (may Allah have mercy on him) said:
This hadith sets a deadline beyond which these things should not be left, but the best is to trim these things before that deadline is reached.
End quote from Al-Ifsah, 5/396.
An-Nawawi (may Allah have mercy on him) said:
As for the time for shaving the pubic hair, the best is to do that when it is needed and the hair has grown long, so when it becomes long, it should be shaved. The same guideline applies to trimming the moustache, plucking the armpit hairs and cutting the nails. Regarding the hadith of Anas that is mentioned in the book – “A time limit was set for us for trimming the moustache, cutting the nails, plucking the armpit hairs and shaving the pubic hair: that was not to be left for more than forty nights” – what it means is: These things should not be left beyond the forty-day deadline; it does not mean that they may be left untouched for forty nights. And Allah knows best.
End quote from Sharh Sahih Muslim, 3/148-149.
III.
The phrase “forty nights”
Does not mean that shaving should be done at night and that counting is only done on the basis of nights.
Rather what is meant by night is the entire day (24 hours).
Ibn al-Jawzi (may Allah have mercy on him) said, commenting on the meanings of the verse
{And (remember) when We appointed for Musa forty nights, and (in his absence) you took the calf (for worship), and you were wrongdoers} [Al-Baqarah 2:51].
He (may Allah have mercy on him) said:
The verse mentions nights and not days because the custom of the Arabs when counting time was to count the nights, as the first day of the month begins at night, since the Arabs referred to the new moon to work out the passage of time. Thus days became secondary to nights.
End quote from Zad al-Masir, 1/80.
Another narration of the hadith of Anas (may Allah be pleased with him) uses the word “days”, as was narrated by an-Nasa’i (14), who said: Qutaybah told us: Ja`far, who is the son of Sulayman, told us, from Abu `Imran al-Jawni, from Anas ibn Malik, who said: The Messenger of Allah (blessings and peace of Allah be upon him) set a time limit for us for trimming the moustache, cutting the nails, shaving the pubic hair and plucking the armpit hairs: we were not to leave that for more than forty days. And on one occasion, he said: forty nights.
The way to work it out should be based on the method that people use nowadays, in which twenty-four hours after shaving is counted as one night having passed, and so on until one reaches forty [nights].
IV.
The scholars differed regarding the ruling on going beyond forty days or nights. According to the Shafa`is, going beyond forty is regarded as disliked (makruh).
An-Nawawi (may Allah have mercy on him) said:
The nails must be cut and the pubic hair must be removed by shaving, plucking, cutting or using a depilatory substance and so on, although shaving is best. And the armpit hair may be removed in one of these ways, although plucking is best for the one who is able to do it. And it is recommended to trim the moustache so that the edge of the lip is clearly visible. In all of these matters, one should begin on the right, and not delay it unnecessarily; it is emphatically disliked to delay it for more than forty days, because of the hadith in Sahih Muslim which says that that is not allowed.
End quote from Rawdat at-Talibin, 3/234.
The Hanbalis hold a similar view. It says in Matalib Uli an-Nuha, 1/87:
If he leaves it for more than forty days, that is disliked, because of the hadith of Anas, who said: A time limit was set for us for trimming the moustache, cutting the nails, plucking the armpit hairs and shaving the pubic hair: that was not to be left for more than forty nights. Narrated by Muslim. End quote.
The Hanafis and some of the scholars are of the view that it is prohibited to go for more than forty days without removing these things that are mentioned in the text.
It says in Hashiyat Ibn `Abidin, 3/66, which is a book of Hanafi jurisprudence:
It says in Sharh al-Munyah and in Al-Mudmarat: It was narrated from Ibn al-Mubarak about cutting the nails and shaving the head in the first ten days of Dhul-Hijjah that he said: You should not delay doing that beyond the timescale mentioned in the hadith [even if that means doing them in the first ten days of Dhul Hijjah], and you should not delay that [until after the first ten days of Dhul Hijjah]. End quote.
It was narrated in Sahih Muslim that the Messenger of Allah (blessings and peace of Allah be upon him) said: “When the first ten days [of Dhul Hijjah] begin and one of you wants to offer a sacrifice (udhiyah), let him not remove any of his hair or cut his nails.” This is to be understood as meaning that it is recommended, not obligatory, according to scholarly consensus. This supports what is mentioned above [ that we should not delay that [until after the first ten days of Dhul Hijjah].
Saying that it is not obligatory to refrain from cutting the hair and so on during the first ten days of Dhul Hijjah does not mean that it is not recommended. So it is recommended not to do that, unless that would mean that you will go beyond the forty-day deadline, because going beyond that is not permissible.
It says in Al-Qunyah: The best is to cut the nails, trim the moustache, shave the pubic hair and clean the body by doing ghusl every week or every fifteen days, and there is no excuse for leaving it beyond forty days, in which case a person would deserve the warning. Doing it weekly is best, doing it every fifteen days is acceptable, and forty days is the maximum limit. End quote.
Shaykh Ibn Baz (may Allah have mercy on him) favoured the view that it is obligatory to remove these things before forty days have passed, as he said: The nails must be cut before forty nights have passed, because the Messenger of Allah (blessings and peace of Allah be upon him) set a time limit for people for cutting the nails, shaving the pubic hair, plucking the armpit hairs and trimming the moustache: these things are not to be left beyond forty nights. This was soundly narrated from the Messenger of Allah (blessings and peace of Allah be upon him)…
End quote from Majmu` Fatawa ash-Shaykh Ibn Baz, 10/50.
The Permanent Committee for Academic Research and Issuing Fatwas was asked about letting the nails grow long, as is common among women nowadays. He replied:
It is not permissible to let the nails grow long, because this is contrary to the sunan al-fitrah which the Prophet (blessings and peace of Allah be upon him) urged us to adhere to, which include cutting the nails.
What is required with regard to cutting the nails, plucking the armpit hairs, shaving the pubic hair and trimming the moustache is not to leave any of these things for more than forty nights, because of the report narrated by Muslim in his Sahih from Anas (may Allah be pleased with him), who said: A time limit was set for us for trimming the moustache, cutting the nails, plucking the armpit hairs and shaving the pubic hair: that was not to be left for more than forty nights. So these women must repent to Allah and give up this bad habit that is contrary to what the Prophet (blessings and peace of Allah be upon him) enjoined. Allah, may He be Glorified and Exalted, says:
{And whatever the Messenger has given you – take it; and what he has forbidden you - refrain from it} [Al-Hashr 59:7]
{So let those who go against his command beware lest some calamity strikes them or a painful punishment befalls them} [An-Nur 24:63].
Permanent Committee for Academic Research and Issuing Fatwas
Bakr Abu Zayd, Salih al-Fawzan, `Abdullah ibn Ghadyan, `Abd al-`Aziz Al ash-Shaykh, `Abd al-`Aziz ibn `Abdillah ibn Baz.
End quote from Fatawa al-Lajnah ad-Da’imah, Vol. 2, 4/60.
Conclusion: the one who leaves these things for more than forty days and does not remove them deliberately, with no valid reason, is going against the teachings of the Prophet (blessings and peace of Allah be upon him) in that regard, and is going beyond the maximum time-limit that he set, and there is the fear that he is sinning if he does that deliberately.
And Allah knows best.