"And He chose David His servant" [Psalm 78:71]. The tribe, I say, of Judah, for the sake of David: but David for the sake of Christ: the tribe then of Judah for the sake of Christ. At whose passing by blind men cried out, "Have pity on us, Son of David:" [Matthew 20:30] and immediately by His pity they received light, because true was the thing which they cried out. This then the Apostle does not cursorily speak of, but does heedfully notice, writing to Timothy, "Be thou mindful, that Christ Jesus has risen from the dead, of the seed of David," etc. [2 Timothy 2:8] Therefore the Saviour Himself, made according to the flesh of the seed of David, is figured in this passage under the name of David, the Lord opening in parables His mouth. And let it not move us, that when he had said, "and He chose David," under which name he signified Christ, he has added, "His servant," not His Son. Yea even hence we may perceive, that not the substance of the Only-Begotten coeternal with the Father, but the "form of a servant" was taken of the seed of David.
[AD 430] Augustine of Hippo on Psalms 78:71