‘And the Pharisees and Sadducees came, and trying him asked him to show them a sign from heaven.'
The coming together of the Pharisees and the Sadducees (linked by one article) may suggest an ungodly alliance between the Galilean Pharisees and the Sadducees at Herod's court (Mark 3:6; Mark 8:15), or it may even suggest an even stronger deputation from the Sanhedrin. Either way all are now united against Him. And they have come to finally test Him out.
The same verb is used here as that used of the tempting by Satan in Matthew 4:1. Satan also had suggested the same kind of sign. Perhaps we are intended to see here that Satan is again tempting Jesus through the Pharisees and Sadducees, and that they are his tools (compare John 8:39-44). They thus demand a sign from Heaven. They do not, of course, expect to receive one. They are out to demonstrate that He is a charlatan.