Sayyidah Aishah Siddiqah (may Allah be pleased with her) says: We have always been hearing that Isaf and Na'ilah were a man and a woman from Jurhum; the two of them committed fornication inside the Ka'bah, so they were transformed into stones.
Al-Bazzar recorded it; its chain contains Ahmad bin Abd al-Jabbar al-Utaridi, who is da'if (weak).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الحج / 5763