Musnad Abu Ya'la al-Mawsili 109:220

Abu Khaythama narrated to us, Yazid bin Harun narrated to us, Hisham informed us, from al-Hasan, from Jabir, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "When you are in a time of plenty, then let the riders take their time, and do not exceed the stages (of the journey). When you are in a time of drought, then hasten, and you must travel by night, for the earth is folded up by night. If the ghouls (spirits) appear to you, then hasten with the Adhan. Do not pray on the main roads, and do not camp on them, for they are the shelters of snakes and beasts of prey. And do not relieve yourselves on them, for they are the places of cursing."