Musannaf Ibn Abi Shayba 13:854

Abu Bakr narrated to us, he said: Zayd ibn al-Hubab narrated to us, he said: al-Zubayr ibn Junada informed me, he said: I asked Salim about a barren land that I bought from someone who owns its title, in which there is nothing. He said: "There is no harm." I said: "Should I pay the *kharaj* (land tax) for it?" He said: "There is no harm." I said: "Should I acknowledge the *sighar* (humiliation/poll tax)?" He said: "That is only upon the heads of men."