“If we are overcome by sloth or by carelessness, if we give ourselves over to dangerous and useless chattering, if we are caught up in worldly cares and in profitless worries, then there will follow in effect from this a harvest of tares to serve as a ministry of death to our hearts. As the Lord and Savior of us all proclaimed, where treasure lies for our works and for our hopes, our hearts will of necessity abide there too.” (cf. Matthew 6:21).
John Cassian (c. 360-435), from his treatise “The Conferences” as recorded in Celebrating the Saints, ed. Robert Atwell (Norwich: SCM Press, 2004) 82.