Sayyidina Abu Hurayrah (RA) reported that some of the sahabah (RA) said,
"O Messenger of Allah, who are they about whom Allah says that if we turn away, they will replace us whereafter they will not be the, likes of us?" He (the narrator) said that Salman was sitting by the side of the Prophet (SAW) and he struck him on his thigh and said, "He his friends. By Him in Whose Hand is my soul, if faith was placed on Pleiades, the people of Persia would fetch it."
[Ahmed 9410, Muslim 2546]
--------------------------------------------------------------------------------