"What the worshipper is commanded to do is be reconciled to the brother. The command "be reconciled" does not mean "put away your enmity or malice." He is not assumed to entertain any malice. Besides, if that is what he is commanded to do, he would not need to leave the altar to do it. He could not be in a better place than in the sanctuary if what he is required to do is to repent and put away his ill will. What the worshipper is commanded to do is something quite different. He is required to leave the altar, to repair to his offended brother, and then to do something. What is it? It is to remove the ground of estrangement or alienation on the part of the brother. Put things right with the brother so that he will not have any reason for grievance; do what is necessary so that there may be the resumption of harmonious relations. The reconciliation as act consists in the removal of the ground of disharmony; the reconciliation as result is the resumption of relations of harmony, understanding, and peace."
His point was a good one. Basically, just to have no ill feelings in your heart toward someone does not mean you're reconciled. You still need to go to the person and bring about the restored relationship. If your relationship, i.e. normal day to day interaction with them, isn't mended, then no matter how at peace your heart may be, you haven't entered into full reconciliation. He distinguishes between the ground of reconciliation, and the restored relationship of reconciliation.
After that section he goes on to show how this is true especially in our reconciliation to God. I thought though that his example from Matthew 5 about how this works out for brothers in Christ was a good (and needed) point in its own right.