Albert Barnes Commentary Isaiah 59:12

"For our transgressions are multiplied before thee, and our sins testify against us; for our transgressions are with us, and as for our iniquities, we know them:" — Isaiah 59:12 (ASV)

Our sins testify against us - Hebrew, ‘Answer against us.’ The idea is that their past lives had been so depraved that they became witnesses against them (compare the notes on Isaiah 3:9).

We know them - We recognize them as our sins, and we cannot conceal from ourselves the fact that we are transgressors.