Musannaf Ibn Abi Shayba 29:79

Ishaq bin Mansur narrated to us, he said: Asbat bin Nasr narrated to us, from al-Suddi, from Abd Khayr, from al-Rabi’ bin Khuthaym, from Abdullah bin Salam: An old Jewish woman fell to his share in the spoils. He passed by the Resh Galuta (Exilarch) and said: "O Resh Galuta, will you buy this slave girl from me?" He spoke to her, and behold, she was of his religion. He said: "For how much?" He said: "For four thousand." He said: "I have no need for her." Abdullah bin Salam swore that he would not lower the price for him. Abdullah bin Salam walked for a while, then he recited this verse: "And if they come to you as captives, you ransom them." He said: "O Abdullah bin Salam, is it you?" He said: "Yes." He said: "You must buy her, or you must depart from your religion." He said: "I have taken her." He said: "Then gift me whatever you wish." So he took two thousand from him and returned two thousand to him.