they.

Mark 7:18
"Are you still so dull?" He asked. "Do you not understand? Nothing that enters a man from the outside can defile him,

Mark 8:17, 18, 21
Aware of their conversation, Jesus asked them, "Why are you debating about having no bread? Do you still not see or understand? Do you have such hard hearts? . . .

Matthew 16:9-11
Do you still not understand? Do you not remember the five loaves for the five thousand, and how many basketfuls you gathered? . . .

Luke 24:25
Then Jesus said to them, "O foolish ones, how slow are your hearts to believe all that the prophets have spoken.

their.

Mark 3:5
Jesus looked around at them with anger and sorrow at their hardness of heart. Then He said to the man, "Stretch out your hand." So he stretched it out, and it was restored.

Mark 16:14
Later as they were eating, Jesus appeared to the eleven and rebuked them for their unbelief and hardness of heart, because they did not believe those who had seen Him after He had risen.

Isaiah 63:17
Why, O LORD, do You make us stray from Your ways and harden our hearts from fearing You? Return, for the sake of Your servants, the tribes of Your heritage.