Herod with his men of war - With his soldiers, or his body-guard. It is probable that in traveling he had "a guard" to attend him constantly.
Set him at nought - Treated him with contempt and ridicule.
A gorgeous robe - A white or shining robe, for this is the meaning of the original. The Roman princes wore "purple" robes, and "Pilate," therefore, put such a robe on Jesus. The Jewish kings wore a "white" robe, which was often rendered very shining or gorgeous by much tinsel or silver interwoven. Josephus says that the robe which Agrippa wore was so bright with silver that when the sun shone on it, it so dazzled the eyes that it was difficult to look on it. The Jews and Romans, therefore, decked him in the manner appropriate to their own country, for purposes of mockery. All this was unlawful and malicious, as there was not the least evidence of his guilt.
Sent him to Pilate - It was by the interchange of these civilities that they were made friends. It would seem that Pilate sent him to Herod as a token of civility and respect, and with a design, perhaps, of putting an end to their quarrel. Herod returned the civility, and it resulted in their reconciliation.

A gorgeous robe - Εσθητα λαμπραν. It probably means a white robe, for it was the custom of the Jewish nobility to wear such. Hence, in Revelation 3:4, it is said of the saints, They shall walk with me in White (garments), because they are Worthy. In such a robe, Herod, by way of mockery, caused our Lord to be clothed; but, the nobility among the Romans wearing purple for the most part, Pilate's soldiers, who were Romans, put on Jesus a purple robe, Mark 15:17; John 19:2; both of them following the custom of their own country, when, by way of mocking our Lord as a king, they clothed him in robes of state. See Bishop Pearce.

And Herod with his (c) men of war set him at nought, and mocked [him], and arrayed him in a gorgeous robe, and sent him again to Pilate.
(c) Accompanied with his nobles and soldiers who followed him from Galilee.

And Herod, with his men of war,.... Or his soldiers, his bodyguards that attended his person, who came with him from Galilee, and were both for his security and service, and for his pomp and magnificence:
set him at nought; made nothing of him; had him in no account; treated him as a silly, and contemptible creature, that could not do any thing that was reported of him; nor able to say any thing for himself; but took him to be a mere fool and idiot; and so they used him:
and mocked him; as a king, and made sport and pastime with him:
and arrayed him in a gorgeous robe. The Vulgate Latin renders it, "a white robe"; a token of his innocence, though not so designed by them, but rather by way of derision, as a symbol of his simplicity and folly. The Syriac version renders it, "scarlet"; and the Arabic and Persic versions, "red". It is very likely that it was an old worn-out robe of one of the officers, or soldiers, which they put on him; in contempt of his being a king, as the Roman soldiers afterwards did, upon the same account:
and sent him again to Pilate; uncondemned, not knowing what to make of him, or the charge against him, and he might be unwilling to have any hand in his death, not having forgotten the case of John the Baptist; and therefore remits him to Pilate, to do as he thought fit with him.

his men of war--his bodyguard.
set him at naught, &c.--stung with disappointment at His refusal to amuse him with miracles or answer any of his questions.
gorgeous robe--bright robe. If this mean (as sometimes) of shining white, this being the royal color among the Jews, it may have been in derision of His claim to be "King of the Jews." But if so, "He in reality honored Him, as did Pilate with His true title blazoned on the cross" [BENGEL].
sent him again to Pilate--instead of releasing him as he ought, having established nothing against Him (Luke 23:14-15). "Thus he implicated himself with Pilate in all the guilt of His condemnation, and with him accordingly he is classed" (Acts 4:27) [BENGEL].
at enmity--perhaps about some point of disputed jurisdiction, which this exchange of the Prisoner might tend to heal.

Herod set him at nought - Probably judging him to be a fool, because he answered nothing. In a splendid robe - In royal apparel; intimating that he feared nothing from this king.