Musnad Abu Ya'la al-Mawsili 108:201

Amr narrated to us, Sufyan narrated to us, from Amr, who said: Jabir narrated to us, [saying]: The Prophet (peace and blessings of Allah be upon him) said: "War is deception." Abu Uthman said: Some of our companions said to me—many of them used to say "War is deception" (al-harbu khud'atun)—but I did not hear it except with the nominative case (raf'): "War is deception" (al-harbu khud'atun).