On the authority of Abu Juhaim (may Allah be pleased with him) who reported that the Messenger of Allah (may the peace and blessings of Allah be upon him) had said:
If anyone who passes in front of a man who is praying knew the responsibility he incurs, he would stand still forty (years) rather than to pass in front of him.
Abu Al-Nadr said: I do not know whether he said forty days or months or years.
(Reported by Al-Bukhari and Muslim)

---

Lessons Deduced:
1. It is forbidden to walk in front of a person who is performing Prayer. If one is praying in a mosque, it is forbidden for anybody to pass between the praying person and the place of his prostration.
2. In places other than the mosque, if the praying person has a cover in front of him, like a stick or a line drawn in the ground, it is forbidden to pass between him and the cover, provided that the distance is not more than one meter and a half.
3. This rule applies to a person who performs whether optional or obligatory Prayer.