Abu Dawud Book 33, Hadith Number 4446.

Narated By Salamah ibn al-Muhabbaq : A similar tradition (to the No. 4445) has also been transmitted by Salamah ibn al-Muhabbaq from the Prophet (PBUH).

This version has: If she asked her to have intercourse with her voluntarily, then she and a similar slave-girl would be given to her mistress from his property.