give the source player to the timer like this
function revivir1()
revivir = 1
cancelText = nil
setPedAnimation(source, ".", ".", -1, false, false, false, true)
outputChatBox (".", source, 255, 0, 0)
setTimer(function(source) -- Pass source player into timer
si = 1
cancelText = cancelText
if (cancelText==nil) then
outputChatBox(".", source, 255, 0, 0) ------This is the wrong text
end
end, 600, 1, source) -- Pass source player into timer
end
addEvent("sistemarev", true)
addEventHandler("sistemarev", root, revivir1)