He chose David also his servant, and took him from the sheepfolds:

Jamieson-Fausset-Brown Bible Commentary

70-72. God's sovereignty was illustrated in this choice. The contrast is striking-humility and exaltation-and the correspondence is beautiful.

Matthew Henry's Concise Commentary

78:56-72 After the Israelites were settled in Canaan, the children were like their fathers. God gave them his testimonies, but they turned back. Presumptuous sins render even Israelites hateful to God's holiness, and exposed to his justice. Those whom the Lord forsakes become an easy prey to the destroyer. And sooner or later, God will disgrace his enemies. He set a good government over his people; a monarch after his own heart. With good reason does the psalmist make this finishing, crowning instance of God's favour to Israel; for David was a type of Christ, the great and good Shepherd, who was humbled first, and then exalted; and of whom it was foretold, that he should be filled with the Spirit of wisdom and understanding. On the uprightness of his heart, and the skilfulness of his hands, all his subjects may rely; and of the increase of his government and peace there shall be no end. Every trial of human nature hitherto, confirms the testimony of Scripture, that the heart is deceitful above all things, and desperately wicked, and nothing but being created anew by the Holy Ghost can cure the ungodliness of any.