Albert Barnes Commentary Daniel 9:13

"As it is written in the law of Moses, all this evil is come upon us: yet have we not entreated the favor of Jehovah our God, that we should turn from our iniquities, and have discernment in thy truth." — Daniel 9:13 (ASV)

As it is written in the law of Moses - The word 'law' referred to all the writings of Moses. See the notes at Luke 24:44.

Yet we did not make our prayer before the Lord our God - Margin, “we did not entreat the face of.” The Hebrew word used here (חלה châlâh) properly means “to be polished;” then to be worn down in strength, to be weak; then to be sick or diseased; then, in Piel (the form used here), to rub or stroke the face of anyone, to soothe or caress, and therefore to beseech or supplicate. See Gesenius, “Lexicon”.

Here it means that, as a people, when they had sinned, they had failed to call upon God for pardon, to confess their sins, to implore His mercy, and to deprecate His wrath.

It would have been easy to turn aside His threatened judgments if they had been penitent and had sought His mercy, but they did not do it. What is said of them here can and will be said of all sinners when the Divine judgment comes upon them.

That we might turn from our iniquities - This means that we might seek grace to turn from our transgressions. And understand Your truth. This refers to the truth which God had revealed, equivalent to saying that they might be righteous.