Musannaf Ibn Abi Shayba 19:141

Abu Bakr narrated to us, he said: Ibn Numayr narrated to us, from Sa’id, from Qatadah, from Sa’id ibn al-Musayyib, regarding a Christian or Jewish woman who is accused of unchastity while she has a Muslim husband and has a child from him. He said: The prescribed punishment (hadd) is upon the one who accuses her.