The heart means love. A good heart means love to the Lord and to the neighbor, while a hard or stony heart means the love of self or the world -- riches and things. When the psalmist asks the Lord to search his heart, he wants the Lord to see what it is that he loves. And we are what we love. What we eat may form our earthly body, but it's only temporary, what we love forms our spiritual body, beautiful or ugly as we have chosen. It's interesting to note that the first multi-cellular motion of our embryo is the pulsating that starts in a twist of blood vessel that is to become our heart, and the last motion of our natural body is our heartbeat. It is there for all of our natural life. And of course there is a beating heart in our spiritual bodies when we come to put them on.

3728. 'And poured oil on the top of it' means holy good [in which it originated]. This is clear from the meaning of 'oil' as the celestial element of love, which is good, dealt with in 886, 3009, and from the meaning of 'the top' as that which is higher, or what amounts to the same, that which is interior - good being that which is higher or interior, and truth that which is lower or exterior, as has been shown in many places. From this one may see what was meant by the ancient practice when people poured oil on the top of a pillar, namely that truth should not be devoid of good but should be grounded in good, thus that good should rule, like the head on top of the body. For truth devoid of good is not truth but is a meaningless sound and the kind of thing that is reduced to nothing. In the next life it is so reduced even with those whose knowledge of truth or matters of doctrine concerning faith, and with those whose knowledge of matters of doctrine concerning love, has been superior to anybody else's, if they have not led a good life and so have not out of a desire for good held on to truth.

[2] Consequently the Church is not the Church by virtue of truth separated from good, nor therefore by virtue of faith separated from charity, but by virtue of truth that is grounded in good, or faith that is grounded in charity. The same is also meant by what the Lord said to Jacob,

I am the God of Bethel, where you anointed a pillar, where you made a vow to Me. Genesis 31:13

Also,

Jacob again set up a pillar, a stone pillar, and poured out a drink-offering over it, and poured oil over it. Genesis 35:14.

'Pouring out a drink-offering over the pillar' means the Divine good of faith, and 'pouring oil over it' the Divine good of love. Anyone may see that unless it meant something celestial and spiritual, pouring oil over a stone would be a ridiculous and idolatrous action.