What is the ruling on delaying the 'Asr prayer until 3:20, knowing that the time for establishing the prayer in the Eastern Province is 2:50, and that this time is unified by the Imam and the congregation (the employees)? And what is the ruling on a group standing in the prayer area who have not prayed, while another group is praying before the unified prayer time?

There is no harm in delaying the prayer beyond its initial time to await the congregation, as long as its preferred time has not ended. The preferred time for the Asr prayer ends when the shadow of everything becomes twice its length. There is no harm for the mosque congregation and its Imam to stand facing the worshippers before the designated time for the Iqamah, in order to await the rest of the congregation. There is no harm for worshippers to form a congregation before the mosque's congregation, with the Imam's permission; otherwise, it is disliked for them to do so. The prayer of all is valid, and it is better for them to pray as one congregation.