In his great collection of sermons on the Sermon on the Mount, Lloyd-Jones has an excellent piece on Matthew 6.19-20.
First of all, what is a treasure that we might have? “‘Treasures’ is a very large term and all-inclusive. It includes money, but it is not money only. …Our Lord is concerned here not so much about our possessions as with our attitude towards our possessions. It is not what a man may have, but what he thinks of his wealth, his attitude towards it. …It is a question of one’s whole attitude towards life in this world. Our Lord is dealing here with people who get their main, or even total, satisfaction in this life from things that belong to this world only. …No matter what it is, or how small it is, if it is everything to you, that is your treasure, that is the thing for which you are living.”
Later in the sermon he asks, “How do we do this in practice?”
Answers: “The first thing is to have a right view of life, and especially a right view of ‘the glory.’ The great fact of which we must never lose sight is that in this life we are but pilgrims. We are walking through this world under the eye of God, in the direction of God and towards our everlasting hope. …If we always think of ourselves in that way, how can we go wrong? Everything will then fall into position.”
Next, says Lloyd-Jones, if we have the view that we’re pilgrims, then “we shall immediately take a right view of our gifts and our possessions. We begin to think of ourselves only as stewards who must give an account of them. …The Christian starts by saying, ‘I am not the possessor of these things; I merely have them on lease, and they do not really belong to me. …I do not cling to these things. They do not become the centre of my life and existence. I do not live for them or dwell upon them constantly in my mind; they do not absorb my life. On the contrary, I hold them loosely; I am in a state of blessed detachment from them. I am not governed by them; rather do I govern them; and as I do this I am steadily securing, and safely laying up for myself, ‘treasures in heaven.'”
From Studies in the Sermon on the Mount (Grand Rapids: Eerdmans, 1976), 353-357.
This book is great, by the way. I use it in my sermon prep with great benefit (though it is well nigh depressing to use, simply because reading it makes me realize my sermons sound like a scared second grader trying to spell “stammer” in front of the large spelling bee crowd!). Anyway, no one should preach/teach the Sermon on the Mount without this book on his/her shelves.