Musnad Ahmad 1139:2

'Abd al-Razzaq narrated to us, Malik informed us, from Abu al-Nadr, from Busr ibn Sa'id, who said: Zayd ibn Khalid sent me to Abu Juhaym al-Ansari to ask him: What did you hear the Messenger of Allah, peace and blessings of Allah be upon him, say regarding the one who passes in front of a person praying? He said: I heard him say: "For him to stand in his place is better for him than to pass in front of the person praying." I do not know whether he said: forty years, or forty months, or forty days.