Musannaf Ibn Abi Shayba 28:972

Abu Mu'awiyah narrated to us, from Ubayd Allah ibn Umar, from Muhammad ibn al-Munkadir, from Rabi'ah ibn Abd Allah ibn al-Hudayr, who said: When Umar would give a horse or a camel to be ridden in the way of Allah, he would say: "When you pass Wadi al-Qura, or a similar place on the road to Egypt, then do with it whatever seems good to you."