Psalms 26:6

I will wash mine hands in innocency— It was a common custom among all the Jews to wash before prayers; but the priests in particular were not to perform any sacred office in the sanctuary till they had poured water out of the laver, and washed their hands in it. David alludes to this custom. But because those outward ablutions might still leave impurities within, which all the water in the world could not wash away, he here declares that he would wash his hands in innocency itself, which he elsewhere calls, the cleanness of his hands, Psalms 18:24. See note on Psalms 7:7.