Albert Barnes Commentary Psalms 35:11

"Unrighteous witnesses rise up; They ask me of things that I know not." — Psalms 35:11 (ASV)

False witnesses did rise up - Margin, "witnesses of wrong." The Hebrew is, "witnesses of “violence”," חמס châmâs. That is, they were persons who, in what they said of me, were guilty of injustice and wrong. Their conduct was injurious to me as an act of "violence" would be.

They laid to my charge - Margin, as in Hebrew: "they asked me." The word "asked" here seems to be used in the sense of "demand;" that is, they demanded an "answer" to what was said. The usage appears to have been derived from courts, where the forms of trial may have involved question and answer. The mode of accusation was in the form of "asking" how a thing was, or whether it was so; and the defense was regarded as an "answer" to such an inquiry. Hence, it is synonymous with our expression of charging anyone, or of accusing anyone.

Things that I knew not - Of which I had no knowledge; which never came into my mind. What those charges were the psalmist does not specify; but it is not uncommon for a good man to be falsely accused, and we are certain that such things occurred in the life of David.