“Do not keep many things for yourself on earth. Insects and rust will spoil them. People will get in and steal them.
But keep things for yourself in heaven. Insects and rust will not spoil them there. People will not get in and steal them.
The place where you keep things is where your heart will be also.” Matt. 6:19-21 WE
Clearly there is more involved in our heavenly "treasure" than Jesus alone. We are also promised "an inheritance incorruptible, undefiled and that does not fade away, reserved in heaven for you . . ." (1 Peter 1:4).
Jesus Himself promises us that "In My Father's house are many mansions"; and that He has gone to prepare a place for us, "that where I am, there you may be also" (John 14:2-3).
We may not know all that awaits us in heaven and I am sure that our inheritance in heaven is greater than what our minds could possibly grasp. But whatever else our inheritance will involve, the most important treasure - our chief treasure - is the Person of Jesus Christ Himself. He Himself will be our greatest joy forever. No other treasure will matter to us above Him.
The point is that, when Jesus is our "treasure", and because He - our treasure - is in heaven, then our hearts are naturally inclined toward the place where He is. When He's our treasure then our hearts move us to seek after Him above all else as our greatest desire on earth.
King David said it very well in Psalm 27, when he wrote, "One thing I have desired of the LORD, that will I seek: That I may dwell in the house of the LORD all the days of my life, to behold the beauty of the LORD, and to inquire in His temple" (vs 4 NKJV).
In Psalm 63, he similarly wrote of how having the Lord as his treasure became his motivation: "O GOD, You are my God; early will I seek You; my soul thirsts for You; my flesh longs for You in a dry and thirsty land where there is no water. So I have looked for You in the sanctuary, to see Your power and Your glory" Psalm 63:1-2 NKJV.
Verse 21 gives us the key to all that Jesus is telling us in this passage. It is a basic principle of life. ". . . Where your treasure is [that is, that place in which is kept that which you most value], there your heart [your devotion, your longing, your desire, the compass-needle of your life] will be also."
The apostle James clearly drew many of his thoughts from the Sermon on the Mount; and among those thoughts was this:
“….. now, you rich people, listen to me! Weep and wail over the miseries that are coming upon you! Your riches have rotted away, and your clothes have been eaten by moths. Your gold and silver are covered with rust, and this rust will be a witness against you and will eat up your flesh like fire. You have piled up riches in these last days.” James 5:1-3 GNT
Jesus urges us not to lay up treasures for ourselves on earth, where moth and rust destroy.