"You anoint my head with oil; my cup runs over." Psalm 23:5b
The Psalmist David knew about shepherding sheep. At the end of the day it was customary for the shepherd to station himself at the door of the sheepfold, where he would examine each sheep as it passed. He would especially examine the head for injuries. When he noticed a sheep with an injury on the head, he would pour a little oil on the wound, thus anointing it. The oil had healing properties, and the sheep would soon be well again.
You anoint my head with oil - After the banquet table, mentioned in verse 5a, there's something the Good Shepherd does for the Psalmist - he anoints his head with oil.
Anointing the head was done for prophets, priests and kings, this act symbolizing the setting apart of the individual for special service. So, in a sense, the Psalmist moves from dining at the Lord's table to serving Him in some capacity. David was anointed king several times during his life.
Further, it can be said that the Psalmist receives the oil from the Shepherd to help heal the wounds inflicted by his enemies (the enemies mentioned in verse 5a) - and David had many enemies!
My cup runs over - David receives so many blessings from the hand of the Shepherd that his cup overflows with blessings. It's good to count one's blessings every now and then. Are you counting yours today?