Praise be to Allah.
There is no saheeh hadeeth that defines the mahr of the hoor al-‘iyn. Everything that has been narrated concerning that is either very weak (da’eef jiddan) or fabricated (mawdoo’), A summary of what has been narrated concerning that from six of the Sahaabah follows:
It was narrated in a marfoo’ report from Ibn ‘Umar (may Allaah be pleased with him) that he said: “How many of the hoor al-‘iyn have a mahr that is no more than a handful of wheat or dates.”
This was narrated by al-‘Aqeeli (1/42) and from him by Ibn al-Jawzi in al-Mawdoo’aat (3/253) and Ibn Hibbaan in al-Majrooheen (1/98). Ibn al-Jawzi said: The one who is accused is Abaan. Abu Haatim Ibn Hibbaan said: Abaan ibn al-Muhbir narrated from trustworthy narrators things that are not their ahaadeeth, so as to confuse even those who have great knowledge. It is not permissible to narrate from him except by way of giving an example of a false hadeeth. He is the one who narrated this hadeeth from Naafi’ and it is baatil (false). al-Daaraqutni said: Abaan is matrook (i.e., his hadeeth is to be ignored). End quote.
Ibn Abi Haatim said in al-‘Ilal (no. 641): My father said: This is a baatil hadeeth. This Abaan is majhool (unknown) and da’eef al-hadeeth. End quote.
Shaykh al-Albaani said in al-Silsilah al-Da’eefah (no. 571): It is mawdoo’ (fabricated).
He also narrated a hadeeth from Abu Hurayrah: “The mahr of the hoor al-‘iyn is a handful dates and a piece of bread.”
This was narrated by Ibn ‘Adiyy in al-Kaamil (5/25) and by Ibn al-Jawzi in al-Mawdoo’aat (3/253). He said: The one who is accused is ‘Umar ibn Subh. Ibn Hibbaan said: He used to fabricate ahaadeeth from trustworthy narrators. It is not permissible to write down his hadeeth except by way of highlighting its strangeness. End quote.
Another hadeeth which is well known among people but is not saheeh is that which is attributed to Anas: “Sweeping the mosque is the mahr of al-hoor al-‘iyn.”
This was narrated by al-Daylami in Musnad Firdaws (no. 4896) and Ibn al-Jawzi in al-Mawdoo’aat (3/253). He said: Its isnaad contains narrators who are majhool (unknown), and ‘Abd al-Waahid is not thiqah (trustworthy). This was also stated by Yahya. Al-Bukhaari, al-Fallaas and al-Nasaa’i said: He is matrook al-hadeeth (i.e., his hadeeth is to be rejected). End quote. Shaykh al-Albaani judged it to be fabricated in al-Silsilah al-Da’eefah (no. 4147).
It is narrated from ‘Ali ibn Abi Taalib (may Allaah be pleased with him) that the Prophet (peace and blessings of Allaah be upon him) said to him: “O ‘Ali, give the hoor al-‘iyn their mahrs: remove harmful things from the road, and take rubbish out of the mosque, for that is the mahr of al-hoor al-‘iyn.”
This was narrated by al-Daylami in Musnad al-Firdaws (no. 8335) and Ibn Shaheen in al-Targheeb fi Fadaa’il al-A’maal (no. 535). In Kanz al-‘Ummaal (16/229) it is attributed to Ibn al-Najjaar. The isnaad of Ibn Shaheen includes al-Ma’aafa ibn Mutahhar and Muwarra’ ibn Jubayr, but I could not find any biography for them, except a few words by Ibn Makula in al-Ikmaal (7/263).
It was also narrated from Abu Umaamah that the Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Handfuls of dates for the poor are the mahrs of al-hoor al-‘iyn.”
This was narrated by al-Daylami in al-Firdaws (no. 4645 and Ibn al-Jawzi in al-Mawdoo’aat (3/253). In Jaami’ al-Ahaadeeth (no. 15093), al-Suyooti attributed it to al-Daaraqutni in al-Afraad.
Ibn al-Jawzi said: It was narrated only by Talhah ibn al-Wadeen. Al-Sa’di said: al-Wadeen is a weak narrator. al-Nasaa’i said: Talhah is matrook (i.e., to be rejected). Ibn Hibbaan said: It is not permissible to narrate from him. End quote.
Al-Albaani judged it to be fabricated in al-Silsilah al-Da’eefah (no. 6197).
A hadeeth about the mahr of al-hoor al-‘iyn was narrated from Abu Qursaafah, whose name was Jandarah: “Taking rubbish out of the mosque is the mahr of al-hoor al-‘iyn.”
This was narrated by al-Tabaraani (3/19), Ibn ‘Asaakir in Tareekh Dimashq (5/110), Abu Bakr al-Shaafa’i in al-Fawaa’id (2/23/2) and Ibn Mandah in al-Ma’rifah (2/259, no. 6340). In al-Durr al-Manthoor (4/144), al-Suyooti attributed it to Abu Bakr al-Shaafa’i in his Rubaa’iyaat. Al-Bayhaqi said in Majma’ al-Zawaa’id (2/113): Its isnaad includes majhool (unknown) narrators. End quote. Shaykh al-Albaani said in al-Silsilah al-Da’eefah (no. 1675): This isnaad is “dark” (i.e., it has many unknown narrators), other than Abu Qursaafah they have no mention in any of the books of men’s biographies, apart from Muhammad ibn al-Hasan ibn Qutaybah, who is proven to be a hafiz and trustworthy. End quote.
To sum up, there is no saheeh hadeeth which defines the mahr of al-hoor al-‘iyn, hence Ibn al-Jawzi (may Allaah have mercy on him) said in al-Mawdoo’aat (3/254):
This hadeeth is not saheeh in any of its isnaads. End quote.
The true mahr of al-hoor al-‘iyn is every good deed that brings one closer to Allaah, and is the cause of entering Paradise.
Al-Qurtubi (may Allaah have mercy on him) said in al-Tadhkirah fi Ahwaal al-Mawtaa wa Umoor al-Aakhirah (p. 556):
Chapter on what is narrated about righteous deeds being the mahr of al-hoor al-‘iyn.
In this chapter he narrated some of the ahaadeeth quoted above, then he said:
Muhammad ibn al-Nu’maan al-Muqari said:
I was sitting with al-Jala al-Muqari in Makkah in al-Masjid al-Haraam, when a tall, lean-bodied old man dressed in rags passed by. Al-Jala got up and stood with him for a while, then came back to us and said: Do you know who this old man is? We said: No. He said: He bought from Allaah a hoor al-‘iyn for four thousand khatmahs (readings of the entire Qur’aan) and when he had completed it, he saw her in a dream, wearing her jewellery and finery. He said: Who are you? She said: I am al-hoor whom you bought from Allaah with four thousand khatmahs; this is the price, what will I get from you? He said: One thousand khatmahs. Al-Jala said: He is still working on that.
It was narrated from Sahnoon that he said: There was a man in Egypt called Sa’eed, and he had a mother who was a devoted worshipper. When he got up at night to pray qiyaam, his mother would pray behind him, and if he grew sleepy his mother would call out to him: O Sa’eed! There is no sleep for the one who fears Hell and wants to marry the beautiful hoor al-‘iyn. So he would get up out of alarm.
It was narrated from Thaabit that he said: My father was one of those who prayed qiyaam to Allaah in the depths of the night. He said: Last night I saw in my dream a woman who did not resemble the women of this world. I said to her: Who are you? She said: A hoor al-‘iyn, a female slave of Allaah. I said to her: Give yourself to me in marriage. She said: Propose to me through your Lord and give me a mahr. I said: What is your mahr? She said: Lengthy tahajjud.
Maalik ibn Dinar said: I had sections of the Quraan that I would read every night. I fell asleep one night and in my dream I saw a beautiful girl, with a piece of vellum in her hand. She said: Can you read? I said: Yes. She gave me the piece of vellum and on it was written these lines of poetry:
You are wasting your time in sleeping rather than seeking high goals
And seeking beautiful hoor al-‘iyn in Paradise.
There in Paradise you will have an eternal life and no death
And you will have delight with the beautiful hoor ‘iyn in splendid pavilions.
Wake up from your sleep, for what is better than sleeping is spending the night reciting the Qur’aan.
Something similar was said by Ibn Rajab in his essay Ikhtiyaar al-Oola (p. 12) and in Lataa’if al-Ma’aarif (p. 159).
See also question no. 10053 about al-hoor al’-iyn.
With regard to cleaning the mosque, it is something that is recommended, and there is a great deal of evidence which encourages that and speaks of its virtue. This has been discussed on our website in the answer to question no. 20160.
And Allaah knows best.