All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
First of all, you should know that according to the view of most scholars, it is permissible to pray Jamaa‘ah (in congregation) at a place other than the Masjid. Therefore, it is permissible for you to pray in congregation at the office after being certain or believing that the time of the prayer has most likely begun.
But is it better to wait to pray with a larger congregation or perform prayer at as soon as its time starts? There is a difference of opinion among the scholars about this. Al-Furoo‘, a Hanbali book, reads: “Is the virtue of performing the prayer at its beginning time better or waiting for a larger congregation? There are two opinions about this.” [End of quote]
In our view, we believe that it is better for you to wait and pray with the Muslim congregation in order to get the reward of performing the prayer in congregation in the Masjid and to respect the difference of opinion of the scholars who are of the view that it is an obligation to pray in congregation in the Masjid, and also so that people would not think ill of you.
This is the view favored by the prominent scholar Ibn ‘Uthaymeen ; he said: “If there are benefits in delaying the prayer to near the end of its time, such as, firstly, not to deviate from the common (lawful) practice of the people, secondly, if there is a large congregation, then this is better.” [End of quote]
For more benefit, please refer to Fatwa 90904.
Allaah Knows best.