Charles H. Spurgeon on Psalms 78:8

As their fathers, a stubborn and rebellious generation. Forasmuch as this bad emulation of their ancestors is with difficulty plucked from the minds of men, because of our innate reverence for our fathers, the prophet heaps up words in the description of the crimes of their fathers. He says they were hrm rwd, that is, a generation detracting from the authority of God, and continually breaking the bonds of the law, and in their petulance shaking off the yoke, as a violent and refractory horse, or an untamed bullock, enduring not the rein, or refusing to yield its neck to the yoke, but constantly drawing back and rejecting the bridle. Mollerus.

Verses 8-9. Look carefully to the ground of thy active obedience, that it be sound and sincere. The same right principles whereby the sincere soul acts for Christ, will carry him to suffer for Christ, when a call from God comes with such an errand. "The children of Ephraim, being armed, and carrying bows, turned back in the day of battle." Why? what is the matter? so well armed, and yet so cowardly? This seems strange: read the preceding verse and you will cease wondering; they are called there, A generation that set not their heart aright, and whose spirit was not steadfast with God. Let the armour be what it will, yea, if soldiers were in a castle, whose foundations were rock, and walls brass; yet if their hearts be not right to their prince, an easy storm will drive them from the walls, and a little scare open their gate, which hath not this bolt of sincerity on it to hold it fast. In our late wars we have seen that the honest hearts within thin and weak works have held the town, when no walls could defend treachery from betraying trust. William Gurnall.