Hadhrat Abu Maleeh reports that he heard Hadhrat Umar (r.a.) say from the pulpit, "There can be no Islaam in the person who does not perform salaah.,,
(Ibn Sa'd, as quoted in Kanzul Ummaal vol.4 Pg.180).
Hadhrat Umar (r.a.) is Roused from his Coma with the Announcement of Salaah
Hadhrat Miswar bin Makhramah (r.a.) reports, I went to see Umar (r.a.) when he was covered in a sheet (and still in a coma after he had been attacked). 'How is he?' I asked. 'Just as you see him (he has not yet roused from his coma),' the others replied. I then said, 'Rouse him with salaah because there is nothing as effective in rousing him as salaah.' The others then called out, 'Salaah, 0 Ameerul Mu'mineen!' 'What!' Hadhrat Umar (r.a.) said with a start, 'By Allaah! I will then have to perform it. There is no part in Islaam for the person who does not perform his salaah.' He then performed his salaah even though blood was flowing from his wound."
Tabraani, reporting from reliable sources as confirmed by Haythami (Vol. I Pg.295).
Another narration from Hadhrat Miswar (r.a.) states that after Hadhrat Umar (r.a.) was stabbed, he fell into a coma. Someone said, "If he is still alive, you will not be able to rouse him with anything more effective in jolting him than with salaah." Someone then said, "Salaah, 0 Ameerul Mu'mineen! The time for salaah has already set in!" Hadhrat Umar (r.a.) regained consciousness and said, ''What! Salaah!? By Allaah! I will then have to perform it. There is no part in Islaam for the person who does not perform his salaah."
Ibn Sa'd (Vol.3 Pg.350).
(From 'Hayatus Sahabah' by Maulana Muhammad Yusuf Khandhlawi)