All this is come upon us - All these calamities. The connecting thought here is, that although all these things had come upon them, yet they could not be traced to their own infidelity or unfaithfulness to God. There was nothing in the national character, there were no circumstances at that time existing, there was no special unfaithfulness among the people, there was no such general forgetfulness of God, and no such general prevalence of idolatry as would account for what had occurred, or as would explain it. The nation was not then more deeply depraved than it had been at other times; but, on the contrary, there was among the people a prevalent regard for God and for his service. It was, therefore, a mystery to the author of the psalm, that these calamities had been suffered to come upon them at that time; it was an event the cause of which he desired to search out, Psalm 44:21.

Yet have we not forgotten thee - As a nation. That is, there was nothing special in the circumstances of the nation at that time which would call down the divine displeasure. We cannot suppose that the psalmist means to claim for the nation entire perfection, but only to affirm that the nation at that time was not characterized by any special forgetfulness of God, or prevalence of wickedness. All that is here said was true at the time when, as I have supposed, the psalm was written - the closing part of the reign of Josiah, or the period immeditely following.

Neither have we dealt falsely in thy covenant - We have not been unfaithful to thy covenant; to the covenant which thou didst make with our fathers; to the commandments which thou hast given us. This can only mean that there was no such prevailing departure from the principles of that covenant as could account for this. The psalmist could not connect the existing state of things - the awful and unique discomfitures and calamities which had come upon the nation - with anything special in the character of the people, or in the religious condition of the nation.

Psalm 44:17 Parallel Commentaries

The Mystery
Of the Woman dwelling in the Wilderness. The woman delivered of a child, when the dragon was overcome, from thenceforth dwelt in the wilderness, by which is figured the state of the Church, liberated from Pagan tyranny, to the time of the seventh trumpet, and the second Advent of Christ, by the type, not of a latent, invisible, but, as it were, an intermediate condition, like that of the lsraelitish Church journeying in the wilderness, from its departure from Egypt, to its entrance into the land …
Joseph Mede—A Key to the Apocalypse