Psalm 23 is undoubtedly the most well-known and well-loved of all the psalms, with its illustration of the Lord as our shepherd. The shepherd's care for his sheep is, internally, describing the things that the Lord does for us in our spiritual journey.

As the psalm unfolds we hear about the Lord’s work for us, during states in our lives when we could be unsure and afraid, and of the Lord’s provision for us. Gradually the psalmist confirms his trust in the Lord’s guidance and declares the many blessings the Lord brings.

This psalm of six verses would surely have been known and loved by the Lord during his life in the world. It would have, for him, been a statement of faith in his purpose to overcome evil and glorify his humanity. Jesus, in states where his human heredity was strong in his mind, would have regarded his own divinity as his shepherd, and seen it as his anchor and provider. For us, spiritually, the same parallel applies -- that our faith in the Lord is to be our trust and guide at all times.

The shepherding care in verses 2 and 3 speaks about how the Lord leads us into acquiring new truths that bring heavenly peace and rest for us. Our state is lifted up and we live in goodness because we understand that this is the divine quality that God wishes for us to live by. (See Apocalypse Explained 375 and Arcana Caelestia 3696)

The valley of the shadow of death describes our states of being afraid, and of not seeing the Lord with us, during which our mind can be filled with disturbing and mocking thoughts. But we know that the Lord is there with us nonetheless. The “rod” and “staff” represent the power of the Lord’s truths for us to use; a rod - used actively to guard the sheep - stands for spiritual truths, and a staff is leaned on, representing natural truths or truths to do with life.”

(Apocalypse Explained 727)

With the provision of truth from the Lord, the psalm shifts to the picture of the bounteous table which truth brings to us as our spiritual nourishment and satisfaction. Our head anointed with oil has many associations of being the Lord’s chosen, of being loved and blessed by the Lord, and of how our mind with its understanding receives love and good to make it full of heavenly joy. “My cup runs over” means the unknown extent of the truths of the Word and the blessings of the Lord. (Apocalypse Explained 727)

The final verse is put in terms of our full conviction of being in the Lord for ever and in all the days of our lives. What we experience and say in terms of time and duration spiritually means what is certain, perpetual and to all eternity. The ‘house of the Lord’ is heaven. (Arcana Caelestia 650)

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.