The Chambers for the Priests (Ezekiel 40:44-46).
‘And outside the inner gate were chambers for the singers in the inner court, which were at the side of the north gate. And their prospect was towards the south, and one at the east gate having the prospect towards the north. And he said to me, “This chamber, whose prospect is towards the south, is for the priests, the keepers of the charge of the house. And the chamber whose prospect is towards the north is for the priests, the keepers of the charge of the altar. These are the sons of Zadok, who, from among the sons of Levi, come near to Yahweh to minister to him.”
There were a number of chambers outside the inner gate, all but two of which were for the singers who sang in the inner court. The two were set aside for the priests, the one facing south (‘this chamber' - being no doubt indicated by the hand of the speaker) for those who had charge of the house (see Ezekiel 44:10-14), the one facing north for those who had charge of the altar (see Ezekiel 44:15-21).
Singers are described elsewhere in 1 Chronicles 6:31-32 where they were Levites, but it may be that the point being made here is that the singers here were priests, (and therefore more holy and allowed into the inner court), the Levites being no longer worthy due to past failure, and that all the chambers facing south were thus for the priests who had the lesser privilege of ‘charge of the house' and of ‘singing'. But only ‘the sons of Zadok' (compare Ezekiel 44:15; 1 Samuel 2:31-33; 2 Samuel 15:24-29; 1 Kings 1:5-26; 1Ki 1:32-35; 1 Kings 2:26-27; 1 Kings 2:35; 1 Chronicles 6:3-8; 1 Chronicles 24:3) were from now on to be allowed to enter the sanctuary and offer the fat and blood of the sacrifices before Yahweh (Ezekiel 44:15). They were the keepers of ‘the charge of the altar'. Thus a distinction was now to be made between differing ‘families' of priests with ‘the sons of Zadok' now stated to be especially favoured because they had shown particular loyalty to Yahweh in the period of the kings (Ezekiel 44:15). There was thus to be a limiting of the priestly function for the majority. See further on Ezekiel 44:10-21.
‘Sons of Zadok' were seen as descended from Zadok of the house of Aaron (1 Chronicles 6:8; 1 Chronicles 6:53), who had loyally supported David, and had ensured the accession of Solomon thereby obtaining the high priesthood (1 Kings 2:35), which remained Zadokite (1 Chronicles 6:10; 1 Chronicles 6:15 with Haggai 1:1) into the future. But loyal Yahwist priests from other parts of the family who sided with their loyal stance may well have joined with them, and been adopted as ‘sons of Zadok', while some of their own who chose the way of idolatry may well have united with others and distanced themselves from the sons of Zadok. For ‘sons of' primarily came to mean ‘those who behaved like' (compare ‘the sons of Belial'). And ‘the sons of Zadok' were probably seen as a narrow-minded clique by other priests.
This enunciation of detail would have been particularly impressive to Ezekiel's hearers, and have helped to convince them that he really had seen the invisible temple of Yahweh already established in the land. The fact that chambers had been so set aside confirmed that God would in the future restore Israel's way of worship. The heavenly temple was conveying a message rather than being for practical utilisation.