Sunan Ibn Majah Book 5, Hadith 144
“The Prophet (ﷺ) said: ‘If
anyone of you knew (how great is the sin involved) in passing in
front
of his brother while he is performing prayer, waiting for one
hundred
years would be better for him than one step that he takes.’”
“What did you hear from the Prophet (ﷺ) about a man when he is performing prayer?” He said: “I heard the Prophet (ﷺ) saying: ‘If anyone of you knew (how great is the sin involved) when he passed 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.”
“The Prophet (ﷺ) was performing prayer at ‘Arafat, and Fadl and I came riding a female donkey. We passed in front of part of the row, then we dismounted and left the donkey, and we came and joined the row.”