When Israel came up out of the Red Sea, they sang praises to God for the mighty deliverance He provided. They must have said to each other, "Never could there be so great a miracle as this! No other generation in all of future history will ever witness so mighty a demonstration of God's power—and in such a visible way.”
David looked back to Israel's miraculous deliverance at the Red Sea and said, "Come and see the works of God: he is terrible [awesome] in his doing toward the children of men. He turned the sea into dry land: they went through the flood on foot: there did we rejoice in him" (Psalm 66:5-6).
Israel was commanded to tell each succeeding generation about God's great miracle-working power on their behalf. They were to use their deliverance at the Red Sea as their example, "shewing to the generation to come the praises of the Lord, and his strength, and his wonderful works that he hath done" (Psalm 78:4).
As a child, David must have sat enthralled as he heard the story told over and over again. Now David told his children the same story: "You know God lives because He took our forefathers through the Red Sea on dry ground. Now, tell it to your children and your grandchildren!" And they did.
It was not enough just to talk about what God had done in the distant past. The psalmist wanted to see God deliver His people now: "We have heard with our ears, O God, our fathers have told us, what work thou didst in their days, in the times of old. How thou didst drive out the heathen with thy hand" (Psalm 44:1-2).
The psalmist is saying here, "Lord, all my life I've heard about what You did in the past, how these incredible scenes of Your glory were visibly manifested to my fathers. My children have heard of it, and now my grandchildren will hear of it."
The psalmist then burst out: "Thou art my King, O God: command deliverances for Jacob" (verse 4). In other words: "But, God, you are my King also. Do these things again for Your people!"
As this psalm was being written, Israel was in a time of great trial. God's people faced a great crisis and they needed a present-day deliverance. So the psalmist came to the Lord with strong reasoning, crying out to the Lord: "Oh, Lord, Your children at the Red Sea may have thought there could never be a crisis like theirs again. We need a powerful manifestation of Your mighty, outstretched arm to deliver. Lord, do it again today!"