Dought & clear, - Ruling on stopping one’sprayer if something serious happens.

If I am praying and someone knocks at the door, and there is no one
else in the house, what should I do? If I stop praying, am I sinning?
Praise be to Allaah.
If a prayer is naafil (supererogatory), there is more room for
manoeuvre, and it is o.k. to stop praying in order to find out who is
at the door. But in the case of a fard (obligatory) prayer, it is not
permissible to stop it unless there is something important which one
is afraid of missing. If it is possible to alert someone else, by
saying "Subhan-Allaah" out loud in the case of men and clapping in the
case of women, so that the person at the door will realize that the
person in the house is busy praying, that will do away with any need
to stop praying. The Prophet(peace and blessings of Allaah be upon
him) said: "Whoever is alarmed by anything whilst praying, let men say
'Subhan-Allaah' and let women clap." (Agreed upon. Al-Bukhaari, 1234;
Muslim, 421).
If it is possible to let the person who is at the door realize that
the person inside the house is praying, by clapping in the case of
women and saying 'Subhan-Allaah' in the case of men, whilst still
praying, this will save you from having to stop the prayer. If that
will not work, because one is too far away from the door or the person
outside will not be able to hear, then it is o.k. to stop the prayer
if necessary, especially if it is a naafil prayer. But in the case of
an obligatory prayer, if it is something important or necessary, and
there is the fear of missing it, it is also o.k. to stop the prayer,
and to repeat it from the beginning. Praise be to Allaah.