‘Jesus said to them, ‘If God were your Father you would love me, for I have come forth and am come from God, and I did not come of my own accord, but he sent me. Why do you not understand what I am saying? It is because you cannot hear my word.'
Jesus now denied what they claimed. He pointed out that their very attitude was clear proof that they were not true children of God, for if they had been they would have loved Him, the One Who came from God at the express will of God. Indeed the reason that they did not understand this was because they did not want to, and it was simply because His preaching was too uncomfortable. It demanded far reaching changes and an acceptance that the system on which they had built their lives might not be as satisfactory as they thought. So the reason why they did not understand Him was simply because their ears were too heavy to hear. ‘Cannot hear my word' means ‘cannot because their prejudice prevents them from hearing it'.
Note His emphasis on the fact that He had not come on His own accord. Later many Pharisees would back some who came on their own accord (first in the final days of Jerusalem and then in the days of Bar Cochba) and it would mean disaster for the Jewish people.