Most of this is a rather didactic psalm. About the only reason we might suggest for finding Psalm 70 tacked on the end (verses 13-17 here) is that it serves as an example of the kind of prayer God answered to justify the first part of this message.
David had no where else to turn. It didn’t matter what he might have felt compelled to do on the human level; if his God was not behind things, nothing would have saved David. He offers the image of being rescued from quicksand or a mud-pit, a sort of wet clay trap, quite deep and with slimy sloped sides. It was quite impossible to escape, even for substantially larger and stronger animals. David says that God allowed his feet to find a rocky extension so he could climb out.
A refreshing rescue calls for a fresh composition, so David sings a new song. The intent was to catch people’s attention with this heartfelt testimony. While it is impossible to overstate God’s trustworthiness, David contrasts that with those who boasted in lies even in small ways. Big talk did not compare well with God’s deliverance. Where does David being? How does he narrow down the vast record of God’s power?
A difficulty in verse 6 is the noteworthy variation between existing manuscripts. The New Testament (Hebrews 10:5) quotes from the Septuagint version of this verse and that is reason enough to prefer it. This places the emphasis on a form of Hebrew parallelism. David says that ritual offerings were never about the offering, but sacrifice itself. A more meaningful sacrifice would be your own obedient flesh while you live, not some dead animal. So David says, “Here I am, Lord! I embrace Your revelation as binding on me!” David sees Covenant Law as a privilege, not a duty.
Such is the message David preaches in the hearing of the nation at every possible opportunity. David felt that was his highest duty as king. Yet he is a king who suffers little from arrogance, because he quickly transitions to calling on God’s mercy as a penitent. For all his royal power, David could not defeat his own sins alone.
In most English translations it is not hard to see how the addition of Psalm 70 fits right in here. With such a feeble moral constitution, David is frantic for God’s delivering hand. He pleads with God as he often does, that his enemies not be allowed to win. David has no fear of death, but worries that an embarrassing end would darken God’s reputation, too. So he asks that God would simply keep on giving His people every excuse to praise His name. They have no where else to turn, either.
