"A wicked and adulterous generation seeketh after a sign; and there shall no sign be given unto it, but the sign of the prophet Jonas. And he left them, and departed." (Matt. 16:4)
This verse reminds me of an adage: "There are none so blind as one who will not see." In the case of the Pharisees and the Saduccees they wanted Jesus to perform some miraculous feat. It was as if they were going to believe on Him, repent of their sin, and be saved. Fortunately the Bible gives us insights into their hearts: "...tempting desired Him that He would shew them a sign..." (v.1) In response, Jesus basically told them that His ressurection would be the only sign that He would show them, to prove to them that they are indeed lost.
The Resurrection occured and some of them (most likely most of them) still refused to acknowledge Jesus to be God's only begotten Son. In Matt. 27:62-66 They requested that Pilate secure the tomb since they feared that Jesus' disciples might steal His body, and that would cause a commotion.
In doing just that, both Pilate and the Pharisees, along with the chief priests sealed their own fate. Because what Jesus said would happen, happened. It is sad to know that despite much of what God has and is doing, unsaved man would rather seal their hearts to their own destruction, than repent and recieve the Savior, who is risen indeed!