Why do monks keep their hands under their habits? 

Brother Michael: There's a ritual on how to do things you do and things you don't do just in your day-to-day acting. This is called a scapular, and when a monk is walking around or whatever, he put the hands under the scapular. There's a way of walking. There are lots of things like that.

What does it symbolize?

Brother Michael: It symbolizes that you're not using. The hands symbolize activity of the person, and a contemplative life is mostly an interior activity, so this symbolizes interior activity. It doesn't mean that all day we're like this. We have lots of things that we have to do, and when we're doing them, the hands are on the outside doing whatever we have to do. But when we're not doing them, the hands go on the inside to signify that the soul is turned on the inside towards God.