Behold, he put no trust in his servants; rather, he putteth no trust' or he putteth not trust. The" servants" intended are those that minister to him directly in heaven, the members of the angelic host, as appears from the parallelism of the other clause of the verse.
Even in them God does not trust implicitly, since he knows that they are frail and fallible, liable to err, etc; only kept from sin by his own sustaining and assisting grace (setup. Job 15:15, where Eliphaz expresses the same belief in his own person).
And his angels he charged with folly; rather, chargeth. The exact meaning of the word translated "folly" is uncertain, since the word does not occur elsewhere. The LXX. renders by σκολιόν τι, "crookedness;" Ewald, Dillmann, and others, by "error."
The teaching clearly is that the angels are not perfect—the highest angelic excellence falls infinitely short of God's perfectness. Even angels, therefore, would be incompetent judges of God's doings.