What is the distance beyond which a person is not sinning if he passes in front of one who is praying?

Question

Praise be to Allah.

The Muslim should try to use something as a sutrah (screen)
in front of him when he is praying. This is a confirmed Sunnah. Some
scholars are of the view that it is obligatory to have a sutrah when
praying.

There is a warning issued to the one who walks in front of a
person who is praying. It was narrated in al-Saheeh that Abu Juhaym
said: The Messenger of Allaah (peace and blessings of Allaah be upon him)
said: “If a person who passes in front of someone who is praying knew (the
burden of sin) that he bears, he would rather stand for forty than pass in
front of him.” Abu al-Nadr said, “I do not know whether he said forty days
or months or years.” (Narrated by al-Bukhaari, al-Salaah, 480;
Muslim, al-Salaah, 507).

With regard to the distance beyond which a person may pass in
front of one who is praying without a sutrah, there are a number of opinions
among the scholars. It is sufficient for us to mention the stronger of these
two opinions. Some of the scholars said that the distance depends on ‘urf
(local custom)

Shaykh Ibn Baaz said: When a person crosses an area which is not directly in
front of the one who is praying and there is no sutrah, he is not sinning,
because if he is far away from him according to what is regarded as far away
in local custom, he is not regarded as one who passes in front of him; this
is like one who passes beyond the sutrah.

Some of the scholars said that the distance in this case is
either three cubits away from where the worshipper is standing, or the space
that a sheep would need to pass in front of the worshipper when he
prostrates. This is the distance prescribed for the sutrah to be in front of
the worshipper, and this is the view of many scholars.

It was narrated that Sahl ibn Sa’d said: Between the place
where the Messenger of Allaah (peace and blessings of Allaah be upon him)
prayed and the wall was a space that would allow a sheep to pass. (Narrated
by al-Bukhaari, 474; Muslim, 508).

It was narrated from Naafi’ that whenever ‘Abd-Allaah ibn
‘Umar entered the Ka’bah, he would walk towards the opposite wall, with the
door behind him. So he would walk towards the wall until he was three cubits
away from it, then he would pray in the place which Bilaal told him the
Prophet (peace and blessings of Allaah be upon him) had prayed. (narrated by
al-Bukhaari, 484).