Mark 8:11-13

The Pharisees came out and began to argue [contentiously and debate] with Him, demanding from Him a sign from heaven, to test Him [because of their unbelief]. He groaned and sighed deeply in His spirit and said, “Why does this generation demand a sign? I assure you and most solemnly say to you, no sign will be given to this generation!” Leaving them, He again boarded the boat and left for the other side.