Sa'id bin al-Musayyab narrates from Sayyiduna Basrah (may Allah be pleased with him), who said: I married a virgin woman who was kept in seclusion, and I found her pregnant. The Prophet (peace and blessings be upon him) said: "The child is your slave. When she gives birth, give her a hundred lashes. And the dowry (mahr) is her right, in return for your having made lawful for yourself (through marriage) relations with her."
Hadith Referenceالمعجم الكبير للطبراني / باب الباء / 1232