What does Psalm 21:10 mean?
By opposing David his enemies destroyed any hope of having a posterity. The Lord will judge the enemies' descendants that undoubtedly repeat the sins of their fathers. Exodus 20:5 records the Lord's warning against those who violate His commandment about idolatry. He warns: "You shall not bow down to [idols] or serve [idols], for I the LORD your God am a jealous God, visiting the iniquity of the fathers on the children to the third and the fourth generation of those who hate me." However, the Lord promises "steadfast love to thousands of those who love me and keep my commandments" (Exodus 20:6).Verses such as this don't suggest that God punishes children for acts committed by their parents. Rather, they mean that imitating the example of prior generations is no excuse. Those who participate in the sins of their parents will be punished for engaging in those sins. Only those who turn away, in repentance, can escape this (Jeremiah 11:10; 25:5).
These verses emphasize the importance of parents modeling faith in the Lord in front of their children. Each generation tends to behave like the preceding generation. Antagonism against the Lord can easily set off a chain reaction that involves several generations and incurs the Lord's judgment.
Psalm 21:8–13 contains the people's address to King David. They express their confidence that he will win future battles because they believe the Lord will swallow up his enemies. This section is similar to the closing section of Psalm 20. Psalm 18:50, 2 Samuel 7:16, and Genesis 12:1–3 guarantee the continuance of the nation of Israel and David's descendants. Psalm 21 ends with a swelling chorus of praise.
Psalm 21 opens and closes with praise to the Lord for the strength He gave David and his army for gaining a victory over the enemy. In verses 1–7 David and the people extol God for answering their prayer and for giving David rich blessings. They rejoice in knowing the Lord is present, and they express their trust in the Lord. They feel safe knowing the Lord's love is unfailing. The people of the congregation voice their assurance that King David will defeat his enemies. David's enemies may plan evil and devise mischief against him, but they will not succeed. David will rout them, and his arrows will strike them. The closing verse of Psalm 21 is a prayer by David and the congregation—it is also a pledge to sing and praise the Lord God for His power.