Is it to be understood from what Ibn ‘Umar and Abu Hurayrah did, and the fact that the people said takbeer when they heard their takbeer, that this was takbeer in unison?

We have previously discussed the ruling on saying takbeer
in unison, and we have quoted the opinions of the scholars concerning
that. We have also stated that quoting the report narrated by al-Bukhaari
in his Saheeh (2/20) – which says that Ibn ‘Umar and Abu Hurayrah
used to go out to the marketplace on the first ten days of Dhu’l-Hijjah
saying takbeer, and the people would say takbeer with their takbeer – to
suggest that it is prescribed to say takbeer in the manner that is done
nowadays, reciting takbeer in unison, is a view that is subject to doubt
and further discussion.

Please see fatwa 127851. 

To sum up: Abu Hurayrah (may Allah be pleased with him) and
Ibn ‘Umar (may Allah be pleased with him) used to go out to the marketplace
and say takbeer in that place where people are usually heedless because they
are distracted, so people will be reminded by the takbeer, and each one will
say takbeer on his own, after that reminder, so the numbers of those who say
takbeer will be many as a result of that. 

This has nothing to do with dividing people into two groups,
or whatever else was mentioned of such made-up things for which there is no
basis in the reports at all. 

With regard to the words of ash-Shaafa‘i in al-Umm
(1/264): When they see the new moon of Shawwaal, I like for the people to
say takbeer in groups and individually, in the mosque, marketplaces, streets
and homes, both travellers and non-travellers, in all situations, wherever
they are, and for them to say the takbeer out loud, and to continue to say
takbeer until they go out to the prayer-place [on the day of Eid al-Adha],
and after sunrise, until the imam comes out for the prayer, then they should
stop saying takbeer. End quote –

this is not speaking of takbeer in unison as it is known
nowadays, in which they all start together and end together, and we have not
come across anything to that effect in the books of his companions, even
though they paid a great deal of attention to details in such matters, to
the extent that they devoted chapters to the “takbeer” or the “takbeer on
the two Eids” in many of their books. 

What appears to be the case, and Allah knows best, is that it
is to be understood as meaning that each one should say takbeer, whether he
is on his own or with a group, all of whom are saying takbeer, in the mosque
or any other place that he mentioned, without them all doing so in unison. 

It is well-known that if the text is ambiguous, in that case
it cannot be used as evidence, therefore what we mentioned in the fatwa
referred to above is not contradicted by any text. 

However we should point out that the view that this kind of
saying takbeer in unison is an innovation is not a recent view; rather it
was stated by leading scholars a long time ago, including Ibn al-Haaj, who
said in his book al-Madhkal (2/285), when discussing the takbeer of Eid:
Moreover they recite takbeer in unison,and that is an innovation, because
what is prescribed is for each person to say takbeer for himself, and not to
say it in unison with others. End quote. 

And Allah knows best.