Give, and it shall be given unto you; good measure, pressed down, and shaken together, and running over, shall men give into your bosom. For with the same measure that ye mete withal it shall be measured to you again. (Luke 6:38)

I think I've understood this scripture better after having worked at the church’s cannery doing dry canning. 

One of the things important to learn while canning is how to get as much food into the can as possible.  Just pouring in the macaroni or the beans or the potato flakes isn’t going to cut it because the particles eventually settle together in a tighter configuration much later after the lid is sealed on.   Settling happens even with powders like sugar or flour. (Maybe you’ve had the experience of opening a food storage can and finding an inch of space between the top of the can and the level of the food.) 

In order to get as much in as possible, you fill it as full as you can, then you shake the can a bit, you bang the bottom on the table gently, and you spin it in your hands, --“pressed down, and shaken together”—and lo!  It settles and there is more room!  So you add more and shake and bang some more and add more until you can’t fit more in.  (You gotta be able to seal the lid on too!)  You want to make sure that whoever gets the cans you packed gets their money’s worth…because you might end up with it!

I don’t think that Jesus had canning specifically in mind when He spoke those words, but He lived in a time when life staples would be measured out by volume, and how much a measure held was dependent upon how hard the measurer tried to fit it in.

The promise that goes with this command to give generously is that the same measure will be meted back to us.  We don’t know how this happens; it is something we have to take on faith that the same charity in our hearts that prompted us to give generously can be activated in others’ hearts to give generously to us.  I’ve experienced this myself, and it was the sort of blessing that it takes a while to notice; it can come from unexpected directions and there’s a bit of a delay… But if you give consistently enough, you start to figure it out.