The Messenger of Allah (s.a.w.s.) said regarding the Martyrs of Uhud :

"They are the ones for whom I testify."

Abu Bakr said:

"Are we not their brothers, O Messenger of Allah (s.a.w.s.)? We accepted Islam like they did and participated in Jehad like them?"

The Messenger of Allah (s.a.w.s.) replied:

"Yes! But I do not know what you (will) do after me."

(Al Muwatta Vol. 2, pg. 462, tradition no. 32 of Kitabul Jehad)