Therefore take heed to your spirit, and let none deal treacherously against the wife of his youth, because He hates
says the LORD God of Israel, and
ḵis-sāh ḥā-mās ‘al- lə-ḇū-šōw
says the LORD of hosts.
Therefore take heed to your spirit, that ye deal not treacherously.
The structure of these verses makes it abundantly clear the prophet is telling his audience there are TWO aspects of their behaviour towards their wives that God hates, and considers treachery:
šal-laḥ - sending forth/putting away.
Malachi 2:14 refers to the marriage covenant (Genesis 2:24 - a man shall cleave/adhere to his wife and they shall be one flesh), and to send her forth would be to break that charge/promise/pledge.
If the husband were to send forth his wife, to whom would she go?
ḵis-sāh ḥā-mās ‘al- lə-ḇū-šōw - covering violence upon his garment.
This is a very interesting expression. Gesenius connects the use of lə-ḇū-šōw here with an Arabic metaphor for wife. The sense of this is: she adorns him and is his pride/glory. To support this idea, there are only two other occurrences of lə-ḇū-šōw in scripture, both of which are used in relation to garments worthy of pride/glory: Job 41:13, where God speaks of Leviathan's impenetrable garment; and Isaiah 63:1, where the prophet speaks of the splendour of the avenger on his way to Jerusalem.
The "violence" to his garment is a clear reference to the violation of conjugal union by the husband, since he will have stolen from his wife the one thing she cannot give to any other man - her innocence/virginity. This aspect of treachery is addressed by Jesus in his Olivet discourse (Matthew 5:32), when he says, "But I say to you that whoever divorces his wife for any reason
except sexual immorality causes her to commit adultery..."
The "covering" of this violence, is a reference to the weeping and crying and pleas for forgiveness that accompany the offerings of these treacherous individuals (Malachi 2:13). God is wearied by their insincerity and the abuse of the means He provided for them to walk "blameless" before him.
I believe the NIV translators have totally missed the covenant aspect of marriage that Malachi draws attention to. They mention the covenant in Malachi 2:14, but then totally mangle the clear reference to the "oneness" of marital union in Malachi 2:15.
Whether or not šal-laḥ refers to legal divorce, the conjugal union of a man and his wife was sealed by a covenant agreement that was supposed to deliver what God seeks - godly offspring. Breaking the covenant would result in the husband, henceforth, begetting ungodly children, and forcing his sent-forth wife to do the same.