Talha ibne-Ubaidullah Radiyallahu anhu narrates
that Rasullullah Sallallahu alaihi wasallam said:
Indeed, I know a Kalimah which if recited by a dying man,
will be a means of solace for his departing soul
and will be a light for him on the Day of resurrection
(this Kalimah is La ilaha illallah).
(Abu Ya’la, Majma-‘uz-Zawaid)