Mukhtasar Bukhari (Abridged) 321 — Sin of passing in front

Narrated from Sayyiduna Abu Juhaim (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) said: "If the one passing in front of a person who is praying knew how much sin he incurs, then surely it would be better for him to stand still for forty ... than to pass in front of him." (Abu Nadr) the narrator of the hadith says: I do not know whether he said forty days, or forty months, or forty years.