Is it a condition to perceive the opening takbir in the first congregation, or can it be in another subsequent congregation, to achieve immunity from hypocrisy and hellfire?

The hadith indicates the virtue of a Muslim praying forty days in congregation, catching the first takbir, whereby he is granted two immunities: immunity from the Fire and immunity from hypocrisy. What is meant by catching the first takbir is catching it with the regular Imam, and not after him or in a second congregation; for that contradicts the intent of the Shari'a in encouraging hastening and early arrival at the mosque.