Maximus of Turin, Homily 60, 3-4
Let us therefore purify our heart, our conscience, and our spirit many days ahead of time, and thus cleansed and spotless let us prepare to receive the immaculate Lord who is coming. As he was born of the Immaculate Virgin, so too may his servants be immaculate to celebrate his birth! Indeed, anyone who is dirty and tainted on that day neither is concerned with the Nativity of Christ nor desires him.
Such a man may well participate bodily in the feast of the Lord, but spiritually he quite distant from the Savoir; nor is it possible for an impure man and a holy man, an avaricious man and a merciful man, a corrupt man and a pure man to be together without the one offending the other, proving himself all the more unworthy the less he is aware of his unworthiness.
Indeed, he causes insult though wishing to be courteous, like the man in the Gospel invited to the feast of the saints who dared to attend the wedding without a wedding garment (see Mt 22:1-14): while all the other guests radiated with justice, faith, and chastity, he alone — with an unclean conscience — was spurned by all the others for the repugnance he caused; and the more the sanctity of the holy guests shone, the more the insolence of this sins was revealed.