The sutrah of a group prayer
During Nightfall group prayers a person passed in front of those praying. One of them signaled to him to prevent him from but he persisted. After prayers, the congregants reproached him. Please clarify the ruling for this.
'Abdullah ibn 'Abbas, may Allah be pleased with them both, said: "I was riding a she-donkey and had at that time I attained puberty. The prophet [pbuh] was leading [the people] in prayer at Mina without a barrier in front of him. So I passed in front of a part of a row [of congregants] and left the animal to graze. I joined a row and no one objected to this" [Bukhari and Muslim].
Commenting on the above hadith, Imam al-Nawawi mentioned in Sharh Muslim: "This hadith demonstrates the validity of the youth's prayer and that the imam acts as a sutrah [barrier] to those praying behind him." The scholar of hadith, Ibn Hajar, stated in Fath al-Bari that ibn 'Abd al-Bar said: 'This hadith of ibn 'Abbas pertains to the hadith narrated by abu Sa'id [which states]: "If any of you is praying, do not allow anyone to pass in front of you.' [However], this injunction applies to the imam and the person who is praying alone. As for those praying behind an imam, there is no harm in [allowing] anyone to pass in front of them as attested to by the hadith narrated by ibn 'Abbas. He [Ibn 'Abd al-Bari] said: 'This is because there is no scholarly contention on this."
Placing a sutrah before oneself during prayer is valid for both the imam and the person praying alone. There is no objection to passing in front of the rows of those praying behind an imam because the imam acts as a sutrah for those praying behind him. This does not mean that it is permissible to pass in front of those praying in congregation without restraint or a necessity. Such a necessity may include a person not being able to reach the place for ablution or his belongings without being able to avoid having to pass in front of congregants, to fill a gap in a row and so forth.
Allah Almighty knows best