Malachi 3 is old covenant- not relevant to the new covenant - might as well go whole-hog and sacrifice animals, too, if they’re stuck in the old covenant.
maybe so but (Imo) the blessing poured out until it overflows in Malachi is NT Acts 2:12-18 And they were all amazed, and were in doubt, saying one to another, What means this? [13] Others mocking said, These men are full of new wine. [14] But Peter, standing up with the eleven, lifted up his voice, and said unto them, You men of Judaea, and all you that dwell at Jerusalem, be this known unto you, and hearken to my words: [15] For these are not drunken, as you suppose, seeing it is but the third hour of the day. [16] But this is that which was spoken by the prophet Joel; [17] And it shall come to pass in the last days, saith God,
I will pour out of my Spirit upon all flesh: and your sons and your daughters shall prophesy, and your young men shall see visions, and your old men shall dream dreams: [18] And on my servants and on my handmaidens
I will pour out in those days of my Spirit; and they shall prophesy:
Acts 10:44-45 While Peter yet spake these words, the Holy Spirit fell on all them which heard the word. [45] And they of the circumcision which believed were astonished, as many as came with Peter, because that on the Gentiles
also was poured out the gift of the Holy Spirit. NT?