Philoxenus of Mabbug

And again when David sheweth concerning the purity of his thoughts he likeneth them unto hands, and their freedom from iniquity he compareth unto the washing of the hands, saying, "I have washed my hands in innocency," that is to say, I have cleansed and purified my thoughts, and I have remembered Thy altar, O Lord. And again he saith, "I by myself have purified my heart, and washed my hands in innocency."