There will be a Time of Trouble at the end of the Gospel Age, which Christians all recognize, but the real end time will be at the end of the Kingdom Age. Only the righteous will survive and live into the ages of ages. All of the wicked will be thoroughly purged out. Therefore, the second coming of Elijah the prophet will be the Second Advent of the Kingdom Age. Spiritually speaking, that work of instructing throughout the Kingdom Age will be successful in converting the world, for those who do not bend the knee and conform will all be rooted out.
As a point of interest, this book is called the “Book of Malachi,” and the word “Malachi” means “my messenger.” Thus this book is a paronomasia, a play on words, used by God to keep the message from being understood too clearly too quickly. Present truth is needed to even begin to scratch the surface.
It is hard to “turn many away from iniquity” if one is not a good example himself of walking properly before God. The priesthood of Malachi’s day was doing the opposite and, consequently, was leading many into iniquity.
Verse 14 is a lesson or caution that comes down to us, for we have made a vow of consecration and we sacrifice unto the Lord. It is easy to criticize others, but we, too, could be guilty of offering “a corrupt [or unacceptable] thing.”