They kept not the covenant of God. This is the reason assigned for the Ephraimites turning their backs in the day of battle; and it explains why the divine assistance was withheld from them. Others, it is true, were guilty in this respect as well as they, but the vengeance of God executed on that tribe, which by its influence had corrupted almost the whole kingdom, is purposely brought forward as a general warning. Since then the tribe of Ephraim, in consequence of its splendor and dignity, when it threw off the yoke, encouraged and became as it were a standard of shameful revolt to all the other tribes, the prophet intended to put people on their guard, that they might not suffer themselves in their simplicity to be again deceived in the same manner. It is no light charge which he brings against the sons of Ephraim: he upbraids them on account of their perfidiousness in despising the whole law and in violating the covenant. Although he employs these two words, law and covenant, in the same sense; yet, in placing the covenant first, he clearly shows that he is speaking not only of the moral law, the all-perfect rule of life, but of the whole service of God, of the truth and faithfulness of the divine promises, and of the trust which ought to be reposed in them, of invocation, and of the doctrine of true religion, the foundation whereof was the adoption. He therefore calls them covenant-breakers, because they had fallen from their trust in the promises, by which God had entered into covenant with them to be their Father. Yet he afterwards very properly adds the law, in which the covenant was sealed up, as it were, in public records. He aggravates the enormity of their guilt by the word refuse, which intimates that they were not simply carried away by a kind of thoughtless or inconsiderate recklessness, and thus sinned through giddiness, want of knowledge or foresight, but that they had purposely, and with deliberate obstinacy, violated the holy covenant of God.

They kept not the covenant of God - The covenant which God had made with the entire Hebrew people. They did not maintain their allegiance to Yahweh. Compare Deuteronomy 4:13, Deuteronomy 4:23; Deuteronomy 17:2.
And refused to walk in his law - Refused to obey his law. They rebelled against him.

They kept not the covenant; of God - They abandoned his worship, both moral and ritual. Thev acted like the Ephraimites in the above case, who threw down their bows and arrows, and ran away.

They kept not the covenant of God,.... Either the covenant of circumcision, which was neglected during their travels through the wilderness, Joshua 5:5 or the covenant made with the people of Israel at Mount Sinai, Exodus 24:7 and this is to be understood not of the children of Ephraim only, but of the Israelites in general, who in many instances broke the covenant, and were not steadfast in it, Psalm 78:37; see Gill on Jeremiah 31:32.
and refused to walk in his law; the law of God, which was given forth by him, by the disposition of angels, through the hands of a mediator, Moses, as a rule of their walk and conversation; but they refused to order their conversation according to it, being unwilling to be subject to it, but despised and cast it away; a sad instance of the corruption of human nature, and the depravity of man's will, boasted of for its freedom, yet what is common, and to be observed in all mankind.