Charles Spurgeon Commentary Mark 8:10-12

"And straightway he entered into the boat with his disciples, and came into the parts of Dalmanutha. And the Pharisees came forth, and began to question with him, seeking of him a sign from heaven, trying him. And he sighed deeply in his spirit, and saith, Why doth this generation seek a sign? verily I say unto you, There shall no sign be given unto this generation." — Mark 8:10-12 (ASV)

Unbelief always pricked him to the heart, and greatly grieved him. When people trusted him, he delighted to exhibit his matchless grace; but when they found fault and questioned, his heart was heavy, and he turned away from them.