Musannaf Ibn Abi Shayba 28:942

Waki’ narrated to us, he said: Hisham al-Dastawa’i narrated to us, from Qatadah, from al-Ahnaf ibn Qays, that ‘Umar stipulated the hospitality of a day and a night, and that they must repair the bridges, and if a man from the Muslims is killed in their land, then his blood money is upon them.