The king is angry. He sees he has been taken advantage of.
Christ has perfectly pictured a situation which teaches all the nuances of the believer’s repentance and transformed life. We can do nothing but ask; we cannot deserve to be let off the enormous debt we owe to God. He forgives us freely and he requires nothing in return for the pardon of all our sins. We cannot give back even a part of what we have received. The first servant unrealistically offered to try to pay back what he owed, but that offer was dismissed as unnecessary and impossible to fulfil. He is to receive a free pardon, but let him understand what has happened. Let him not carry on, with his debt now forgiven, as if he had received nothing. Many people would like the removal of their guilt and would like to avoid going to hell, but few are ready to turn from their sin and begin to serve and obey God in earnest. There is always a tendency to take advantage of grace without letting it change us, but God will not allow us to receive it on this basis. He reads our hearts and knows if we are genuine. There is no way into the kingdom of heaven without coming on God’s terms.