It was narrated from Busr bin Sa'eed that Zaid bin Khalid sent word to Abu Juhaim Al-Ansari asking him: "What did you hear from the Prophet P.B.U.H about a man who passes in front of another man when he is performing prayer?" He said: "I heard the Prophet P.B.U.H saying: 'If anyone of you knew (how great is the sin involved) when he passes in front of his brother who is performing prayer, then waiting for forty:"' (one of the narrators) said: "I do not know if he meant forty years, forty months, or forty days, 'would be better for him than that." (Sahih)