A reminder not to raise one's voice in conversation in front of those who are praying.

The Shaykh : And there is another reminder; some of our brothers drew your attention to it just now; and that is that you should not raise your voices in conversation with one another. This advice was well-placed, and the response to it was a double error; because the one giving advice ordered not to raise voices so as not to disturb those who are praying; whether their prayer is voluntary or it is an obligatory prayer that they missed in the mosque; so we must note here two matters: one is that it must be a continuous, ongoing requirement; this place should not be one where voices are raised; whether there is someone praying or not; because this is part of the etiquette of gatherings. The other matter is: striving to perform the obligatory prayer in the mosque; if it is missed, there is no harm in gathering here while waiting for the lesson to begin, so that those who missed the obligatory prayer can pray, either alone or with a group of those in the same situation.
This is the reminder, and it benefits the believers, if Allah wills.