'A Christian who is pure is upon earth like a bird that is kept fastened down by a string. Poor little bird! it only waits for the moment when the string is cut to fly away.
Good Christians are like those birds that have large wings and small feet, and which never light upon the ground, because they could not rise again and would be caught. They make their nests, too, upon the points of rocks, on the roofs of houses, in high places. So the Christian ought to be always on the heights. As soon as we lower our thoughts towards the earth, we are taken captive.'
St. Jean Marie Baptiste Vianney, the Cure of Ars
This brings to mind
But seek the kingdom of God, and all these things shall be given you besides. Luke 12:31
or
For where your treasure is, there also will your heart be. Luke 12:34