Mark 8:11-12 NLT

11 When the Pharisees heard that Jesus had arrived, they came to argue with him. Testing him to see if he was from God, they demanded, "Give us a miraculous sign from heaven to prove yourself."
12 When he heard this, he sighed deeply and said, "Why do you people keep demanding a miraculous sign? I assure you, I will not give this generation any such sign."