My soul shall be satisfied - See the notes at Psalms 36:8. The idea is, that his soul now longed for the service of God as one who is hungry longs for food, or as one who is thirsty longs for drink; and that the time would come when this longing desire would be satisfied. He would engage in the service of God as he desired to do; he would be permitted to enjoy that service without interruption.
As with marrow and fatness - See the notes at Psalms 36:8. The words here employed denote rich food; and the comparison is between the pleasure of serving God, and the satisfaction derived from food when one is hungry. It is not uncommon to compare the pleasures of religion with a feast or banquet. Compare Isaiah 25:6.
And my mouth shall praise thee with joyful lips - Lips full of joy; or, which give utterance to the joy of the heart.