Musannaf Ibn Abi Shayba 9:1634

Waki’ narrated to us, from Sufyan, from al-Shaybani, from al-Sha’bi, who said: If a man accuses his wife of adultery before he has consummated the marriage with her, he must perform the *li’an* (oath of imprecation), and she is entitled to half of the dowry.