Do you think it is unfair that people who marry and have sex are forever bound to that marriage when people who do not marry and fornicate are not bound to that person? If you think so, then you do not understand covenanting.
When you covenant with God and abandon that relationship, the Bible says your second state is worse that the first.
“20If indeed they have escaped the corruption of the world through their knowledge of the Lord and Savior Jesus Christ, only to be entangled and overcome by it again, their final condition is worse than it was at first.” 2 Pet 2:20.
Is that unfair that leaving the covenant puts one in a worse state that the original lost state? If so, then you do not understand covenanting.
Marriage is for life and Jesus says, “What God has joined together, let no man separate.” Mt 19.
Jesus doesn’t say that about anything but marriage. God created marriage and no man gets to criticize God’s justice of making it difficult to escape from.
In Malachi, what was the treachery being committed? What does God hate? Do you think God hates small things?
The sexual sins of fornication, homosexuality, and adultery are all sins that separated men from God. They are sexual sins, but they are not the same sins. This is obvious by what the Hebrews writer said, “Marriage is to be held in honor among all, and the marriage bed is to be undefiled; for fornicators and adulterers God will judge.” Heb. 13:4.
The marriage bed is the only place that sexual intimacy is allowed by God. And men who sleep with women just for sex to abandon them will suffer their own judgment from God unless they repent. But the goal is marriage. God created marriage for the creation of family, for the safe and healthy environment in which to raise children, and for the stability of society itself. Marriage is a blessed covenant that comes with special responsibilities and to say this is unfair is to not understand covenanting.