We may read in the sahih sunnah the following narration:
Once on a very cold and stormy night, Ibn 'Umar pronounced the Adhan for the prayer and then said, "Pray in your homes." He (Ibn 'Umar) added. "On very cold and rainy nights Allah's Messenger (ﷺ) used to order the Mu'adh-dhin to say, 'Pray in your homes.' "
(Source Sahih al-Bukhari, see also in al-Muwatta' and Sahih Muslim and different versions in Sahih al-Bukhari -with the addition of travel- in Sahih Muslim -with a repetition of the statement- and one explicitly denying its' repetition etc.)
As I've never witnessed this in practice I'd like to get some more details and the views of scholars of fiqh especially on the following points:
The call of adhan usually contains the words:
Come to prayer حَىَّ عَلَى الصَّلاَةِ
which seems to contradict to:
Pray in your homes ألا صلوا في الرحال
does the mua'adhhin in that case calls for the prayer saying "come to prayer" twice as usual or is the "Pray in your homes" a replacement for that? And when exactly should the mu'addhin make this addition in the order of adhan?
If a mu'addhin made this call does it mean there's no congregation held at the mosque? Or does it mean they will pray congregation, but not expect a gathering of the people or will they join to prayers at one time?
What are the conditions for making this addition according to scholars of fiqh?