Charles H. Spurgeon on Psalms 78:61

And delivered his strength into captivity, etc. He calls the ark the strength of God, not because the virtue of God was shut up therein, or was so bound to it that he could not, unless through it, be powerful and strong: but because his presence, whose symbol the ark was, had always revealed its virtue and might to Israel, in the perpetual defence and various deliverances of that people. After the same manner he calls it the beauty or glory of God, because God by his own presence declared his glory among the people, and desired that it should be conspicuous by this external symbol. Mollerus.