Ezekiel 44:15
But the priests the Levites, the sons of Zadok, that kept the charge of my sanctuary when the children of Israel went astray from me, they shall come near to me to minister unto me, and they shall stand before me to offer unto me the fat and the blood, saith the Lord GOD:
The priests who were Levites descended from Zadok held fast to responsibility for the holy dwelling place at the time the rest of the people wandered away from God. Their steadfastness in guarding what had been entrusted to them set them apart in a season of general unfaithfulness.
Because they had remained loyal, they were granted the privilege of drawing close to God to serve Him directly and of taking their stand in His presence to present the choicest portions and the lifeblood of the offerings. That nearness included entering into the sacred house itself, coming up to His table, and continuing to guard His appointed order. By contrast, the other Levites who had turned aside were shut out from acting as priests in close attendance upon the holy things. The distinction shows that God demands unwavering loyalty and consecrated character from those who minister for Him, and that He upholds the dignity and purity of His sanctuary.