God is looking for righteous offerings from His servants.
"He will sit as a refiner and a purifier of silver; He will purify the sons of Levi, and purge them as gold and silver, that they may offer to the Lord an offering in righteousness." Malachi 3.3 announces the coming of Jesus as Lord and Savior. He would refine the children of Levi like gold and silver.
Levi was the tribe of Israel chosen to serve Almighty God as priests. They would perform the special duties of the Tabernacle, and later in the Temple.
At first Levi and his sons felt honored to dedicate themselves to the Lord. They did it with holiness and fear. Only they could carry the Ark of the Covenant, assemble and disassemble the Tabernacle, making sacrifices and present the people’s offerings to God, in addition to other duties.
But over time, his children grew cold in their faith and did what was evil. They no longer served God.
Their lack of fear caused them to look at offerings as a weariness. They showed disrespect for the Lord of Hosts by giving Him unclean offerings… stolen, lame and sick animals. Malachi 1.13
Jesus came as a refiner's fire to purify the unclean hearts of the sincere, and refine them like gold. But this can only be performed on the sincere because all others, hypocrites and so forth, would be burned up by His fire.
The blood of Jesus continues to wash and justify a sincere sinner, and the fire of His Spirit keeps him pure so that he brings righteous offerings to the Lord.