Deuteronomy 21:6
4 and bring the heifer down to a wadi with flowing water, to a valley that is neither plowed nor sown. There at the wadi they are to break the heifer’s neck. 5 Then the Levitical priests will approach (for the Lord your God has chosen them to serve him and to pronounce blessings in his name, and to decide every judicial verdict) , 6 and all the elders of that city nearest the corpse must wash their hands over the heifer whose neck was broken in the valley. 7 Then they must proclaim, “Our hands have not spilled this blood, nor have we witnessed the crime. 8 Do not blame your people Israel whom you redeemed, O Lord, and do not hold them accountable for the bloodshed of an innocent person.” Then atonement will be made for the bloodshed.
Psalm 73:13
11 They say, “How does God know what we do? Is the Most High aware of what goes on?” 12 Take a good look. This is what the wicked are like, those who always have it so easy and get richer and richer. 13 I concluded, “Surely in vain I have kept my motives pure and washed my hands in innocence.25 14 I suffer all day long and am punished every morning.” 15 If I had publicized these thoughts, I would have betrayed your people.
Notes and References
"... The psalmist declares that he has nothing in common with the worthless (literally “idol worshippers”), hypocrites, and the wicked (verses 4-5; 1:1, 4-5). If the speaker is a priest, this is a protest that he has not given in to idol worship. Verses 6-7 describe the ritual and oath of purification and the altar procession. Washing of hands symbolizes integrity (24:4) or innocence (Deuteronomy 21:6-7; Psalm 73:13; Matthew 27:24-26) ..."
Waltner, James H. Psalms (p. 143) Herald Press, 2006