I came across this expression while I was reading "Asgard Stories". This is a dialogue between Heimdall, guardian of Bifrost, the "trembling bridge", and Odin. Because of his good work, Odin says very nice things about him.
It is well for us that we have such a faithful guardian of the "trembling bridge"; if it were not for you, Heimdall, our enemies might long ago have taken Asgard by storm. You are so watchful, you can hear the grass grow in the fields, and the wool gather on the backs of the sheep, and you need less sleep than a bird. I myself stand in great wisdom, in order to take care of such faithful servants, and to drive back such wicked enemies!
I can't really understand it. I don't know if this is en idiom or not. If you could tell me another way of saying it or something like that, I'd appreciate it.