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.

683. As regards the use twice of the verb 'did' comprehending both good and truth, it should be recognized that in the Word, especially the Prophets, one matter may be described in two ways, as in Isaiah,

He has passed on in peace, a way He has not gone with His feet. Who has performed and done this? Isaiah 42:3, 4.

Here the first statement has regard to good, the second to truth, that is to say, the first regards things of the will, the second those of the understanding. Thus 'passing on in peace' embodies things of the will, 'a way he did not go with His feet' those of the understanding. The same applies to 'performing' and 'doing'. In the Word things that belong to the will and to the understanding, that is, to love and faith - or what amounts to the same, celestial things and spiritual things - are joined together in such a way that each individual part images a marriage, and answers to the heavenly marriage. The same applies here with the repetition of the same verb.