(in the pure Tradition of the Prophet pbuh)
It is best for husband and wife not to sleep after having sex until they first perform wudhuu’. There are various hadith about this, among them:
First: On the authority of ‘Aa’shah (rada) who said: “Whenever the Prophet (pbuh) wished to sleep or eat while in a state of Janaba (i.e. after having sex and before bathing), he would wash his private parts and perform wudhuu’ as for prayer.” [Al-Bukhaaree and Muslim].
Second: On the authority of Ibn ‘Umar (rad) who said: “O Messenger of Allah (pbuh), should we go to sleep in a state of janaba?” The Prophet (pbuh) answered: “Yes, after making wudhuu.” [Al-Bukhaaree and Muslim]. In another version: “Perform wudhuu’ and wash your private parts, and then sleep.” [Al-Bukhaaree and Muslim]. And, in another version: “Yes, you can perform wudhuu’, sleep, and bathe whenever you want.” [Muslim and al-Baihaqi]. And, in still another version: “Yes, and perform wudhuu’ if you wish.” (This last version proves that this wudhuu’ is not obligatory.) [Ibn Khuzima and Ibn Hibban: Saheeh].
Third: On the authority of ‘Ammaar ibn Yaasir (rad), the Prophet (pbuh) said: “There are three which the angels will never approach: The corpse of a disbeliever; a man who wears perfume of women; and, one who has had sex until he performs wudhuu’.” [Abu Dawood, Ahmad and others: Hasan].