Musannaf Ibn Abi Shayba 28:464

'Abdah ibn Sulayman narrated to us, from 'Ubayd Allah, from Nafi', from Ibn 'Umar, who said: 'Umar said: "Do not leave the Jews and the Christians in Medina for more than three days, [which is] the amount of time for them to sell their goods." And he said: "Two religions shall not coexist in the Arabian Peninsula."