God shows here that he is not pacified by the vain excuses which hypocrites allege, and by which they think that the judgment of God himself can be turned away. We see what great dullness there is in many, when God reproves them, and brings to light their vices; for they defend themselves with vain and frivolous excuses, and think that they thus put a restraint on God, so that he dares not urge them any more. In this way hypocrites elude every truth. But God here testifies, that men are greatly deceived when they thus judge, by their own perception, of that celestial tribunal to which they are summoned; I, he says, know Ephraim, and Israel is not hid from me There is to be understood an implied contrast, as though he said, that they were ignorant of themselves; for they covered their vices, as I have said, with frivolous excuses. God testifies that his eyes were not dazzled with such fine pretenses. "How much soever, then, Ephraim and Israel may excuse themselves, they shall not escape my judgment: vain and absurd are these shifts which they use; I indeed am not ignorant." Let us then learn not to belie, by our own notions, the judgment of God; and when he reproves us by his word, let us not delude ourselves by our own fancies; for they who harden themselves in such a state of security gain nothing. God sees more keenly than men. Let use then, beware of spreading a veil over our sins, for God's eyes penetrate through all such excuses. That he names Ephraim particularly, was not done, we know, without reason. From that tribe sprang the first Jeroboam: it was therefore by way of honor that the name of Ephraim was given to the ten tribes. But the Prophet names Ephraim here, who thought themselves superior to the other tribes, by way of reproach: I know them, and Israel is not hid from me He afterwards expresses what he knew of the people, which was, that Ephraim was wanton, and that Israel was polluted; as though he said "Contend as you please; but you will do so without profit: I have indeed my ears stunned by your lies; but after you have adduced everything, after you have sedulously pleaded your own cause, and have omitted nothing which may serve for an excuse, the fact still will be, that you are wantons and polluted." In short, the Prophet confirms in this second clause what I have before stated, that men, when they flatter themselves, deceive themselves; for God in the meantime condemns them, and allows no disguise of this kind. Israel and Ephraim gloried, then, in their superstitions, as though they held God bound to them: "This is wantonness," he says, "This is pollution." The Prophet indeed does here cut off the handle from all those self-deceptions which men use as reasons, when they defend fictitious forms of worship; for God from on high proclaims, that all are polluted who turn aside from his word.

I know Ephraim - There is much emphasis on the "I." It is like our, "I have known," or "I, I, have known." God had known him all along, if we may so speak. However deep they may have laid their plans of blood, however they would or do hide them from man, and think that no eye seeth them, and say, "Who seeth me? and who knoweth me? I, to whose eyes all things are naked and opened Hebrews 4:13, have all along known them, and nothing of them has been hid from Me. For, He adds, even now, now when, under a fair outward show, they are veiling the depth of their sin, now, when they think that their way is hid in darkness, I know their doings, that they are defiling themselves. Sin never wanted specious excuse. Now too unbelievers are mostly fond of precisely those characters in Holy Scripture, whom God condemns. Jeroboam doubtless was accounted a patriot, vindicating his country from oppressive taxation, which Rehoboam insolently threatened. Jerusalem, as lying in the Southernmost tribe, was represented, as ill-selected for the place of the assemblage of the tribes. Bethel, on the contrary, was hallowed by visions; it had been the abode, for a time, of the ark.
It lay in the tribe of Ephraim, which they might think to have been unjustly deprived of its privilege. Daniel was a provision for the Northern tribes. Such was the exterior. God says in answer, "I know Ephraim." "Known unto God are all his works from the beginning of the world" Acts 15:18. Although (in some way unknown to us) not interfering with our free-will, known unto God are our thoughts and words and deeds, before they are framed, while they are framed, while they are being spoken and done; known to Him is all which we do, and all which, under any circumstances, we should do. This he knows with a knowledge, before the things were. : "All His creatures, corporeal or spiritual, He doth not therefore know, because they are; but they therefore are, because He knoweth them. For He was not ignorant, what He was about to create; nor did He know them, after He had created them, in any other way than before. For no accession to His knowledge came from them; but, they existing when and as was meet, that knowledge remained as it was." How strange then to think of hiding from God a secret sin, when He knew, before He created thee, that He created thee liable to this very temptation, and to be assisted amidst it with just that grace which thou art resisting! God had known Israel, but it was not with the knowledge of love, of which He says, "The Lord knoweth the way of the righteous" Psalm 1:6, and, "if any man love God, the same is known of Him, but with the knowledge of condemnation, whereby He, the Searcher of hearts, knows the sin which He judges" 1-Corinthians 8:3.

I know Ephraim - I know the whole to be idolaters.

I know (d) Ephraim, and Israel is not hid from me: for now, O Ephraim, thou committest whoredom, [and] Israel is defiled.
(d) They boasted themselves not only to be Israelites, but also Ephraimites, because their King Jeroboam came from that tribe.

I know Ephraim, and Israel is not hid from me,.... Though they may cover their designs from men, and seek deep to hide their counsel from the Lord, and make plausible pretences for what they do, and put on an appearance of religion; yet God, who knows all men, and their hearts, cannot be deceived; he judges not according to outward appearance; all things are naked and open to him; nor can any hide themselves from him; he knows their persons, intentions, and designs, as well as actions. Kimchi interprets Ephraim of Jeroboam, the son of Nebat, who was of that tribe; others, of the tribe itself, and Israel of the other nine tribes; others take Ephraim for the ten tribes, and Israel for the two tribes: but it is best to understand Ephraim and Israel of the same, even of the ten tribes; whose works, as the Targum paraphrases it, the Lord knew, particularly what follows:
for now, O Ephraim, thou committest whoredom; both corporeal and spiritual adultery, which frequently went together, as observed in the preceding chapter: the Lord knew their corporeal whoredom, though ever so secretly committed, and their spiritual adultery or idolatry, under all the specious pretences of worshipping him; which was an abhorrence to him, as well as a pollution to them:
and Israel is defiled; with the same sins; for all sin is of a defiling nature, and especially those mentioned, which defile body and soul, and render men loathsome and abominable in the sight of God.

Ephraim--the tribe so called, as distinguished from "Israel" here, the other nine tribes. It was always foremost of the tribes of the northern kingdom. For four hundred years in early history, it, with Manasseh and Benjamin, its two dependent tribes, held the pre-eminence in the whole nation. Ephraim is here addressed as foremost in idolatry.
I how . . . not hid from me--notwithstanding their supposed profound cunning (Hosea 5:2; Revelation 2:2, Revelation 2:9, Revelation 2:13, Revelation 2:19).
now--"though I have been a rebuker of all them" (Hosea 5:2) who commit such spiritual whoredoms, thou art now continuing in them.

"I know Ephraim, and Israel is not hid from me: for now, O Ephraim, thou hast committed whoredom; Israel has defiled itself. Hosea 5:4. Their works do not allow to return to their God, for the spirit of whoredom is in them, and they know not Jehovah." By עתּה, the whoredom of Ephraim is designated as in fact lying before them, and therefore undeniable; but not, as Hitzig supposes, an act which has taken place once for all, viz., the choice of a king, by which the severance of the kingdoms and the previous idolatry had been sanctioned afresh. נטמא, defiled by whoredom, i.e., idolatry. Their works do not allow them to return to their God, because the works are merely an emanation of the character and state of the heart, and in their hearts the demon of whoredom has its seat (cf. Hosea 4:12), and the knowledge of the Lord is wanting; that is to say, the demoniacal power of idolatry has taken complete possession of the heart, and stifled the knowledge of the true God. The rendering, "they do not direct their actions to this," is incorrect, and cannot be sustained by an appeal to the use of נתן לב in Judges 15:1 and 1-Samuel 24:8., or to Judges 3:28.