Musnad Ahmad 1245:2

'Affan narrated to us, he said: Hammad bin Zayd narrated to us, he said: Budayl bin Maysarah narrated to us, from al-Mughirah bin Hakim, from Safiyyah bint Shaybah, from a woman among them, that she saw the Prophet, may Allah bless him and grant him peace, from a small window while he was hastening in the bottom of the watercourse, and he was saying: "The valley is not crossed except by hastening." And I think he said: And the garment had uncovered his knees. Then Hammad said afterwards: "It is not crossed," or he said: "The Abtah (valley floor) is not crossed except by hastening." And I heard him say: "The Abtah is not crossed except by hastening."