comma not necessary at all but if you still want to use it, use after "çocuğu".

in some extreme thinking, "çocuğu ağlar halde" may be an adjective of a sad woman. the woman was left in the street with her crying child! meaning is not this but 1 out of a 1000 may think this, to prevent misunderstanding we can use comma after "cocuğu".

if we use "çocuğu sokakta ağlar halde", comma not necessary.

finally we express this with or without comma like below:

Çocuğu sokakta ağlar halde bıraktılar.

or with comma

Çocuğu, ağlar halde sokakta bıraktılar.

1. You think a comma is not necessary at all.

2. You are telling me where I can use one.

YOU DONT KNOW WHAT YOU ARE TALKING ABOUT

Pay attention, word order isn´t same in these sentences.
if we change the word order as if in second sentence, it may be necessary.