Jer 17:9
The heart is deceitful above all things, and desperately corrupt; who can understand it?
You are quoting the scripture out of context, not understanding it correctly. When considered in its proper context, it has a different meaning than the one you have assigned to it. This is the full context (with comments added in braces):
Jeremiah 17:
5 Thus saith the Lord; Cursed be the man that trusteth in man, and maketh flesh his arm, and
whose heart departeth from the Lord.
6 For he shall be like the heath in the desert, and shall not see when good cometh; but shall inhabit the parched places in the wilderness, in a salt land and not inhabited. {This is a metaphor for losing, or the withdrawal of the Spirit of God from the wicked, whose actions are described in verse 5. See verse 8 for a continuation of the same metaphor.}
7 Blessed is the man that
trusteth in the Lord, and whose hope the Lord is. {This verse is in opposition to verse 5, which refers to the wicked, i.e. those “…whose heart departeth from the Lord”.}
8 For he shall be as a tree planted by the waters, and that spreadeth out her roots by the river, and shall not see when heat cometh, but her leaf shall be green; and shall not be careful in the year of drought, neither shall cease from yielding fruit. {This verse is a metaphor for receiving the inspiration of heaven—i.e. the Holy Ghost. The “waters of the river” is a metaphor for the Holy Ghost (see John 7:38).}
9 The
heart {that is to say, the heart of the wicked man, as discussed above, not of the righteous man} is deceitful above all things, and desperately wicked: who can know it?
10 I the Lord
search the heart {i.e. of the wicked as well as the righteous}, I try the reins, even to
give every man according to his ways, and according to the fruit of his doings. {i.e. you receive your reward according to what is in your heart—either good or bad.}
11 As the partridge sitteth on eggs, and hatcheth them not; so he that getteth riches, and not by right, shall leave them in the midst of his days, and at his end shall be a fool. {He is still continuing the same theme as before. The context remains the same. The wicked are the ones “whose heart depart from the Lord”.}
To sum it up, it is the heart of the
evil and the wicked, those whose hearts
"depart from the Lord," that is wicked and deceitful, and as a parched ground, because the Spirit of God has departed from it, and it is incapable of receiving the inspiration of heaven. By contrast, the heart of the righteous is full of light and the inspiration of heaven, as a
"watered garden" (Isa. 58: 11; Jer. 31:12); and is not deceitful, but can discern between truth and falsehood, right and wrong. The Lord in the NT has also taught the same doctrine, but in different words:
John 7:
17 If any man will do his will {i.e. God’s will}, he shall know of the doctrine, whether it be of God, or whether I speak of myself.
Why is it that “doing the will of God” will enable a man to “know of the doctrine, whether it be of man or of God”? For the same reason that Jeremiah has described—because doing the will of God will put the heart of man in the right condition for it to receive that divine Spirit by which he will be able to discern between the right and the wrong, the true and the false—what is of God and what is not of God. Modern LDS scripture too affirms the same doctrine:
D&C 50:
24 That which is of God is light; and he that receiveth light,
and continueth in God, receiveth more light; and that light groweth brighter and brighter until the perfect day.
D&C 88:
67 And if your eye be
single to my glory {i.e. striving to do the will of God with single-mindedness}, your whole bodies shall be filled with light, and there shall be no darkness in you; and that body which is filled with light
comprehendeth all things.
God will not dwell in unholy temples, but only in the
hearts of the righteous will he dwell:
1 Corinthians 3:
16 Know ye not that ye are the temple of God, and that the Spirit of God welleth in you?
17 If any man defile the temple of God,
him shall God destroy; for the temple of God is holy, which temple ye are.
Alma 34:
36 And this I know, because the Lord hath said he dwelleth not in unholy temples, but in the hearts of the righteous doth he dwell;…
zerinus
Continued . . . /