Thou hast made void the covenant of thy servant - Thou hast dealt with him as if there were no such covenant; as if no such promise had been made to him. The word rendered "made void," means to abhor, or reject.
Thou hast profaned his crown, by casting it to the ground - literally, "Thou hast profaned to the earth his crown;" that is, Thou hast treated it as a polluted thing; a thing to be rejected and abhorred; a thing which one casts indignantly upon the ground.

Thou hast (d) made void the covenant of thy servant: thou hast profaned his (e) crown [by casting it] to the ground.
(d) Because of the horrible confusion of things, the prophet complains to God, as though he did not see the performance of his promise and thus discharging his cares on God, he resists doubt and impatience.
(e) By this he means the horrible dissipation and tearing of the kingdom which was under Jeroboam, or else by the Spirit of prophecy Ethan speaks of those great miseries which came to pass soon after at the captivity of Babylon.

Thou hast made void the covenant of thy servant,.... His servant David the Messiah, Psalm 89:3, meaning not the covenant of circumcision, nor the covenant at Sinai, which were really made void at the death of Christ; but the covenant of grace and redemption made with Christ, which it was promised should stand fast, and never be broken, Psalm 89:3, but was thought to be null and void when the Redeemer was in the grave, and all hopes of redemption by him were gone, Luke 24:21, but so far was it from being so, that it was confirmed by the sufferings and death of Christ; and every blessing and promise of it were ratified by his blood, hence called the blood of the everlasting covenant, Hebrews 13:20,
thou hast profaned his crown by casting it to the ground: by suffering it to be cast to the ground, and used contemptibly; as when Jesus was crowned with thorns, and saluted in a mock manner; when an "if" was put upon his being the King of Israel, Matthew 27:29, and which seemed very inconsistent with the promise, Psalm 89:27 that he should be made higher than the kings of the earth; and yet so it was, and is; he is highly exalted, made Lord and Christ, crowned with glory and honour, and is set far above all principality and power, and every name that is named in this world or that to come, notwithstanding all the above usage of him.

An insult to the "crown," as of divine origin, was a profanation.