Pilate appealed to the crowd (Matt 27:15, Mark 15:6) with this proposal to release Jesus, and not to the chief priests, because he knew what their answer would be. Pilate was trying to get the best of both worlds. If he succeeded in his ploy to get the people to request the release of Jesus he could do so (which he wanted to do) without officially acquitting Him. In this way he would be placing the blame for the release of Jesus on the crowd and thus still be pleasing the chief priests, because Jesus would still be officially guilty. At the same time, Pilate’s only release at the festival would be an innocent man and not anyone who really was guilty of breaking Roman law. Pilate even uses the title “the King of the Jews” in an effort to sway the crowd in Jesus’ favor. Pilate probably figured this was a foolproof plan since the people had recently shown that Jesus was highly favored among them (John 12:12-19). Pilate’s fear of men and wish to gain favor with them will cause “him to stain his judge’s robe with innocent blood, from which he vainly sought to cleanse his hands.” (Maclaren) See (Matt 27:24).

Matthew 27:15  Now it was the governor’s custom at the Feast to release a prisoner chosen by the crowd.

Mark 15:6  Now it was the custom at the Feast to release a prisoner whom the people requested.

John 12:12-19  The next day the great crowd that had come for the Feast heard that Jesus was on his way to Jerusalem.  They took palm branches and went out to meet him, shouting, “Hosanna!” “Blessed is he who comes in the name of the Lord!” “Blessed is the King of Israel!”  Jesus found a young donkey and sat upon it, as it is written,  “Do not be afraid, O Daughter of Zion; see, your king is coming, seated on a donkey’s colt.”  At first his disciples did not understand all this. Only after Jesus was glorified did they realise that these things had been written about him and that they had done these things to him.  Now the crowd that was with him when he called Lazarus from the tomb and raised him from the dead continued to spread the word.  Many people, because they had heard that he had given this miraculous sign, went out to meet him.  So the Pharisees said to one another, “See, this is getting us nowhere. Look how the whole world has gone after him!”

Matthew 27:24  When Pilate saw that he was getting nowhere, but that instead an uproar was starting, he took water and washed his hands in front of the crowd. “I am innocent of this man’s blood,” he said. “It is your responsibility!”

This practice was one of mercy and the release of a condemned man honored the Passover which was a memorial to the release of Israel from the bondage of Egypt, but it was also an injustice and possibly injurious to the public (Prov 17:15). Pilate lacked the courage and integrity to release the innocent Jesus on the merit of the lack of evidence against Him.

Proverbs 17:15  Acquitting the guilty and condemning the innocent—the LORD detests them both.