Chapter 70:4 & 5
The Evening Service
4. The prayers from Boruch A-d-o-n-o-i l'olom... until Yir'u should be
recited while sitting.*
* {In Eretz Yisrael, it is customary to omit these prayers entirely.}
It is forbidden to interrupt one's prayers from the beginning of the
evening service - the prayer V'hu rachum - until the conclusion of the
Shemoneh Esreh. Nevertheless, the sexton's announcement of the prayers
Ya'aleh v'yovo and Tal u'motor is not considered to be an interruption,
because it is necessary for the prayer service itself.
5. When one member of the congregation prolongs his prayers in the evening
service in the synagogue, his colleagues should wait for him to conclude
his prayers [before leaving], lest they disrupt his concentration.
If he began his prayers at a time when it was impossible for him to
conclude together with the congregation, the latter are not required to
wait for him. It is clear that he entered with this thought and is not
afraid [of being left alone].*
* {Nevertheless, a pious person should wait even under such circumstances
(Misgeres Hashulchon 6).}