Musar zu Bereschit 45:1

The reason for the bells on the rim of the robe of the High Priest is specifically spelled out in the Torah. His voice (approach) should be heard when he entered the Sanctuary. This was in the nature of securing permission before entering the Sanctuary. Anyone entering suddenly, i.e. unannounced, was guilty of death. We know of something similar in the palace of Ahasverus (Esther 4,11). I shall explain this in greater detail when I deal with Leviticus 16,17: "No one is to be in the Tent of Meeting when Aaron enters to obtain atonement in the Sanctuary." This is why the Torah commanded that he had to announce his arrival. It is not unlike the time Joseph revealed himself to his brothers. He had instructed that everyone present in the palace had to be removed first, except for himself and his brothers (Genesis 45,1). Service to the King has to be performed with no one else present. When one leaves the king one must also be granted permission so that the king's servants will know when to re-enter the king's presence. An additional dimension which is important when dealing with the presence before the King of Kings is that unless permission has been obtained both before entering and before leaving, G–d's angels are apt to kill the person who acts without permission. The Torah warns Aaron so that we may appreciate that if even a person of the exalted stature of Aaron is subject to such restrictions, anyone on a lower level does not even have to be warned specifically. When the Torah adds the words לפני ה', in 28,39, it adds stature to Aaron who is compared to an angel of the Lord of Hosts. According to our sages the reason there must not be a tear in the robe (28,31), i.e. that it should be constructed in such a way that it is not liable to be torn, is because Satan is jealous of the High Priests's stature and tries to pull him by his robe as warriors do.

Bereshit Rabbah 93, 9 commenting on Genesis 45,1 "Joseph could not control himself," has Rabbi Chama bar Chaninah say that Joseph acted carelessly by instructing everybody to leave the room when he wanted to reveal himself to his brothers; had one of them kicked him he would have died. Rabbi Shmuel bar Nachman says that Joseph acted prudently. He was well aware of the righteousness of his brothers and did not suspect them of being or becoming guilty of bloodshed. He was certain that the brothers would not even kill an Egyptian who had framed them (they considered him an Egyptian). He certainly did not suspect them of wanting to kill their own brother who was a צדיק, a pillar of the elitist society of the world!