A priest is chosen among men and appointed to act on behalf of men in relation to God, to offer gifts and sacrifices for sins. Like any other men, he too is a sinner and beset with weakness.
Because of this he is bound to offer sacrifice for his own sins as well as for those of the people. He should not take honor upon himself but only for God who called upon him.
His model is Christ who did not exalt himself to be made a hight priest but was appointed by God who said to him, "Thous art my Son, today I have begotten thee".
