Mark 6:52

52 for they had not understood about the loaves; their hearts were hardened.

Read Mark 6:52 Using Other Translations

For they considered not the miracle of the loaves: for their heart was hardened.
for they did not understand about the loaves, but their hearts were hardened.
for they still didn’t understand the significance of the miracle of the loaves. Their hearts were too hard to take it in.