Adam Clarke on Psalms 23:6

Goodness and mercy shall follow me - As I pass on through the vale of life, thy goodness and mercy shall follow my every step; as I proceed, so shall they. There seems to be an allusion here to the waters of the rock smitten by the rod of Moses, which followed the Israelites all the way through the wilderness, till they came to the Promised Land. God never leaves his true followers providential mercies gracious influences, and miraculous interferences, shall never be wanting when they are necessary. I will dwell in the house, ושבתי veshabti, "and I shall Return to the house of the Lord," for ever, לארך ימים leorech yamim, "for length of days." During the rest of my life, I shall not be separated from God's house, nor from God's ordinances; and shall at last dwell with him in glory. These two last verses seem to be the language of a priest returned from captivity to live in the temple, and to serve God the rest of his life.