According to some narrations, before Hazrat Abu Bakr (radhiyallahu ‘anhu) commenced dictating the letter, he said to Hazrat ‘Uthmaan (radhiyallahu ‘anhu), “Give me mashura and advise me regarding who I should appoint as the Khalifah, for by Allah, in my sight, you are also worthy of the position of Khilaafah.” Hazrat ‘Uthmaan (radhiyallahu ‘anhu) replied, “I will write the name of Hazrat ‘Umar (radhiyallahu ‘anhu)” and he then commenced writing the letter. However, when he reached the point where the name of Hazrat ‘Umar (radhiyallahu ‘anhu) had to be written, Hazrat Abu Bakr (radhiyallahu ‘anhu) fell unconscious. Since Hazrat ‘Uthmaan (radhiyallahu ‘anhu) knew that Hazrat Abu Bakr (radhiyallahu ‘anhu) wanted Hazrat ‘Umar (radhiyallahu ‘anhu) to be the next Khalifah, he wrote his name.
Thereafter, when Hazrat Abu Bakr (radhiyallahu ‘anhu) regained consciousness, he specified, “Write the name of Hazrat ‘Umar (radhiyallahu ‘anhu).”
(Hayaatus Sahaabah 2/ 31-33)