Psalms 78:9

9.The children of Ephraim being armed, and shooting with the bow. The sacred writer sets before us an example of this unfaithfulness in the children of Ephraim. As those who are pertinaciously set upon doing evil are not easily led to repentance and reformation by simple instruction, the punishments with which God visited the children of Ephraim are brought forward, and by these it is proved that they were reprobates. Since they were a warlike people, it was an evidence of the divine displeasure for them to turn their backs in battle. And it is expressly declared, that they were skillful in shooting with the bow; (317) for it is an additional stigma to represent such as were armed with weapons to wound their enemies at a distance as fleeing through fear. From this, it is the more abundantly manifest that they had incurred the displeasure of God, who not only deprived them of his aid, but also made their hearts effeminate in the hour of danger.

Here the question may be raised, Why the children of Ephraim only are blamed, when we find a little before, all the tribes in general comprehended in the same sentence of condemnation? Some commentators refer this to the slaughter of the sons of Ephraim by the men of Gath, who came forth against them to recover their cattle of which they had been despoiled, 1 Chronicles 7:20. (318) But this exposition is too restricted. Perhaps the kingdom of Israel had fallen into decay, and had been almost ruined when this psalm was composed. It is therefore better to follow the opinion of other interpreters, who think, that by the figure synecdoche, the children of Ephraim are put for the whole people. But these interpreters pass over without consideration the fact, which ought not to be overlooked, that the Ephraimites are purposely named because they were the means of leading others into that rebellion which took place when Jeroboam set up the calves, (1 Kings 12:25.) What we have already said must be borne in mind, that towards the close of the psalm, the rejection of the tribe of Ephraim is, not, without cause, contrasted with the election of the tribe of Judah. The children of Ephraim are also here spoken of by way of comparison, to warn the true children of Abraham from the example of those who cut themselves off from the Church, and yet boasted of the title of the Church without exhibiting holy fruits in their life. (319) As they surpassed all the other tribes in number and wealth, their influence was too powerful in beguiling the simple; but of this the prophet now strips them, showing that they were deprived of the aid of God.