Do not store up for yourselves treasures on earth, where moth and rust destroy, and where thieves break, in and steal. But store up for yourselves treasures in heaven, where moth and rust do not destroy, and where thieves do not break in and steal. For where your treasure is, there your heart will be also. (Matt. 6:19-21)The first verse has to do with where your treasure is, on earth or heaven. Where that treasure is, that is where your heart is. The second verse is talking about the storehouse of your heart and what you put in it. What is stored up in your heart determines what comes out of your mouth.
You brood of vipers, how can you who are evil say anything good? For out of the overflow of the heart the mouth speaks. The good man brings good things out of the good stored up in him, and the evil man brings evil things out of the evil stored up in him. (Matt. 12:34-35)
Since, then, you have been raised with Christ, set your hearts on things above, where Christ is seated at the right hand of God. Set your minds on things above, not on earthly things. (Col. 3:1-2)