Isaiah 32:1

Behold, a king shall reign in righteousness, and princes shall rule in judgment.

A king is to reign in righteousness, and princes under him are to rule in just judgment.
That reign is a shelter and a refreshment to the vulnerable and weary, bringing clearer sight and hearing and understanding.
Under it the vile person is unmasked as vile, and the generous is recognized as generous.

The promised king is Christ, who brought righteousness and judgment and peace to the human family.
He did this by taking humanity upon Himself and by teaching obedience to God.
The salvation He provides is laid hold of through the merits of His crucifixion and resurrection.