Jamieson, Fausset and Brown on Ezekiel 40:47

47. court, an hundred cubits ... foursquare--not to be confounded with the inner court, or court of Israel, which was open to all who had sacrifices to bring, and went round the three sides of the sacred territory, one hundred cubits broad. This court was one hundred cubits square, and had the altar in it, in front of the temple. It was the court of the priests, and hence is connected with those who had charge of the altar and the music. The description here is brief, as the things connected with this portion were from the first divinely regulated.