Adam Clarke's Commentary on the Bible

Verse 5 (Psalms 23:5)

Thou preparest a table before me - Here the second allegory begins. A magnificent banquet is provided by a most liberal and benevolent host; who has not only the bounty to feed me, but power to protect me; and, though surrounded by enemies, I sit down to this table with confidence, knowing that I shall feast in perfect security. This may refer to the favor God gave the poor captive Israelites in the sight of the Chaldeans who had grievously treated them for seventy years; and whose king, Cyrus, had not only permitted them now to return to their own land, but had also furnished them with every thing requisite for their passage, and for repairing the walls of Jerusalem, and rebuilding the temple of the Lord, where the sacrifices were offered as usual, and the people of God feasted on them.

Thou anointest my head with oil - Perfumed oil was poured on the heads of distinguished guests, when at the feasts of great personages. The woman in the Gospel, who poured the box of ointment of spikenard on the head of our Lord (see Matthew 26:6 , Matthew 26:7 ; Mark 14:8 ; Luke 7:46 ;), only acted according to the custom of her own country, which the host, who invited our Lord, had shamefully neglected.

My cup runneth over - Thou hast not only given me abundance of food, but hast filled my cup with the best wine.

- Adam Clarke's Commentary on the Bible