מוסר אויף שמות 30:1

There is yet another altar above the one on which the archangel Michael offers the souls of the righteous, just as there were two altars in the Tabernacle on earth. There is an outer and an inner altar. When the Torah gives the measurements of these two altars we are told that they should be square (Exodus 27,1 and 30,1). This is strange since the Torah had already given the measurements of both the front and the sides of these altars, i.e we know that they were to be square. The extra words רבוע, square, may therefore be understood as an allusion to the corresponding altars in the Heavenly Sanctuary. The "outer" altar in the Heavens corresponds to the encampment of the Israelites in the desert which was square and which was guarded by the four angels Michael, Gabriel, Uriel and Raphael. The "upper" altar in the Heavens was supported by the four חיות which Ezekiel saw in his vision in which he was shown the מרכבה (Ezekiel chapter 1). This is where the crown of the good name is at home. The crown of priesthood is immediately below. The border or crown around the Altar represents the righteous in the World to Come who sit around the table wearing their crowns and enjoying the splendour of G–d's presence.