齋三日乃見其所為齋者。
When a person purifies himself for three days, one can then see what his conception of purification is.
祭之日，將入戶，僾然若有見乎其容。
On the day of sacrifice, when he is about to enter the gate, he will have every semblance of looking directly at the countenance of the deceased person. On going out after having made several circuits of the space inside, he will look as if there were a sound of sighing in his ears.
盤旋出戶，喟然若有聞乎嘆息之聲。
The visage of the deceased is constantly before his eyes; the voice of the deceased, even with its characteristic pauses and throat clearings, is constantly in his ears; and the preferences and dislikes of the deceased are constantly in his heart.
先人之色，不絕於目；聲音咳唾，不絕於耳；嗜欲好惡，不忘於心。
是則孝子之齋也。
This is the way a filial son engages in purification.