Question: AssalamuAlaykum O-rahmatullah O-barokatuh!  

When some one is praying can we cross?
Give me some proofs of the hadith, JazacAllah-khair!
Assalamu'Alaykum O Rahmatullah O Barokatuh!

Answer: 
The narration below indicates that we are commanded to pray behind a Barrier/Sutrah:

> 
> If the one who is praying has set up a sutrah (object to serve as a
>  screen). In this case it is permissible to pass beyond the sutrah,
>  because the Prophet (peace and blessings of Allaah be upon him) said:
>  “If any one of you prays, let him face towards something. If he cannot
>  find anything, then let him set up a stick. If he cannot do that, then
>  let him draw a line, then it will not matter if anyone passes in front
>  of him.”
> 
> 
> 

Not quite sure if prayer is interrupted by any one passing infront or is it only those mentioned below:

> 
> The hadeeth of Abu Hurayrah (may Allah be pleased with him) who said:
>  The Messenger of Allah (blessings and peace of Allah be upon him)
>  said: “Prayer is interrupted by a woman, a donkey and a dog, but
>  something like the back of a saddle protects against that.” Narrated
>  by Muslim (511).
> 
> 
> 

However it does seem to be sinful to pass in front of someone praying anyways whether it was one of the above or not, therefore it is better to avoid doing so:

> 
> Prophet (peace and blessings of Allaah be upon him) said: “If the one
>  who passes in front of a person who is praying knew what (a burden of
>  sin) he bears, it would be better for him to stand for forty rather
>  than pass in front of him.” Abu’l-Nadar – one of the narrators – said:
>  I do not know whether he said forty days or months or years. Narrated
>  by al-Bukhaari, 510; Muslim, 507 – from Abu Juhaym (may Allaah be
>  pleased with him).
> 
> 
> 

If one happens to be placing a barrier while another tries to pass him then he is to prevent him from passing through:

> 
> Indeed, al-Bukhaari (487) and Muslim (505) narrated that Abu Sa‘eed
>  al-Khudri (may Allah be pleased with him) I heard the Messenger of
>  Allah (blessings and peace of Allah be upon him) say: “If one of you
>  prays facing towards something that is screening him from the people,
>  and someone wants to pass (directly) in front of him, let him push him
>  away, and if he insists then let him fight him, for he is nothing but
>  a devil.”
> 
> 
> 

However there happens to be a [scholarly opinion](https://islamqa.info/en/26182) that if the distance is greater than that which is needed to prostrate then one does not have to prevent people from passing. (I have not investigated this in detail)
Default rule: If there's a sutra (barrier like a pole of hands height) then any male can pass.

In congregation prayer one can pass in front of anybody except the imam irrespective of barrier.