Komentarz do Sanhedryn 2:3

אינו יוצא מפתח פלטרין שלו – for it is a disgrace for the king to show his grief before the people.

If any of his near kin die he may not go out of the door of his palace. Rabbi Judah says: “If he wishes to follow the bier he may, since we have found that David followed the bier of Avner, as it says, “And King David followed the bier” (II Samuel 3:31) They answered, “That was only to appease the people.”
When they feed him the funeral meal all the people sit on the floor and he sits on a couch.
Mishnah three discusses the procedures of mourning if a king’s family member dies.
This mishnah deals with funeral procedure when one of the king’s near relatives dies. Although there is no prohibition in the Torah against the king participating in funerals, the Sages did not think it respectful for a king to be seen in a state of mourning. Rabbi Judah again finds biblical precedent for the king to participate in the funeral (as he found precedent for the king to marry another king’s widow in mishnah two). When during the battles between the House of Saul and the House of David, Avner, Saul’s army commander, was murdered by Joab, the commander of David’s army for having killed Joab’s brother, David goes out after Avner’s bier. According to Rabbi Judah this is precedent for any king. The Sages reply to Rabbi Judah that David only did so to appease the people so that they wouldn’t say that Joab killed Avner with David’s permission. In other, normal, cases it is forbidden for the king to participate in the funeral procession.
When the people feed the king his funeral meal, they sit on the floor, to show their participation in his grief and he sits on a couch, since he is not allowed to truly mourn. Note that the high priest was allowed to sit on a low stool. The Sages were less concerned about the respect shown for the high priest than they were for the respect shown towards the king.

לפייס את העם – in order that they should know that it was not at the David’s advice that Joab should kill Avner [son of Ner, the military commander of Saul] (See 2 Samuel 3:37). And the Halakha is not according to Rabbi Yehuda.

דרגש – bed