Imam Zeynel Abidin (as) and importance of recommended (Nawafil) prayers

Once Imam Zeynel Abidin (as) was in the middle of his prayer when his
cloakrolled down from his shoulder but he remained unconscious about
it. When he finished his prayer one ofhis companions asked: 'Oh son of
the Holy Prophet (saw)! While youwere offering prayer your clock
rolled down but you did not pay attention to it.'
Imam Zeynel Abidin (as) replied: 'Woe upon you! Do you know in front
of whom I was standing? Such awareness prevented me from paying
attention towardsmy cloak. Don't you understand that a servant's
prayer is accepted only to the extent he pays attention towards
Almighty Allah (SWT) during his prayer?'
The companion commented: Oh son of the Holy Prophet (saw), Therefore,
on this basis we all are going to be doomed?
Imam Zeynel Abidin (as) replied: No! If you offer recommended
(Nawafil) prayers, Almighty Allah (SWT) through them will treat your
obligatory (Wajib) prayers as completed.